Mn Codoped AgNbO3 Lead-Free Antiferroelectric Ceramics with

Subscriber access provided by The University of Texas at El Paso (UTEP)

Article

La/Mn co-doped AgNbO3 lead-free antiferroelectric ceramics with large energy density and power density Chenhong Xu, Zhenqian Fu, Zhen Liu, Lei Wang, Shiguang Yan, Xuefeng Chen, Fei Cao, Xianlin Dong, and Genshui Wang ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.8b02821 • Publication Date (Web): 29 Oct 2018 Downloaded from http://pubs.acs.org on October 29, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 23 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Sustainable Chemistry & Engineering

La/Mn co-doped AgNbO3 lead-free antiferroelectric ceramics with large energy density and power density Chenhong Xu,†,‡ Zhengqian Fu, Chen, †Key

†

†,‡

Zhen Liu,

†

Lei Wang,

†,‡

Shiguang Yan,

†

Xuefeng

Fei Cao,† Xianlin Dong,† Genshui Wang†,*

Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese

Academy of Sciences, 1295 Dingxi Road, Shanghai 200050, People’s Republic of China ‡University

of Chinese Academy of Sciences, Beijing 100049, P. R. China

AUTHOR INFORMATION Corresponding Authors *E-mail: [email protected]

KEYWORDS: Silver niobate; lead-free ceramics; antiferroelectric; energy storage; power density

1 ACS Paragon Plus Environment

ACS Sustainable Chemistry & Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 23

ABSTRACT: Dielectric materials with high energy density have attracted much attention due to their potential applications in modern electronics and electrical power system. In this work, a large energy storage density of 3.2 J/cm3 was achieved in La/Mn co-doped AgNbO3 antiferroelectric ceramics through enhancing the ferroelectricantiferroelectric backward transition field and reducing the remnant polarization simultaneously. Moreover, the coexistence of Mn2+/Mn3+ at A-site disrupts the randomly disordered Nb5+ at high temperature, leading to the disappearance of freezing temperature Tf. This results in a stable antiferroelectric phase M2 over a broad temperature and thus a good temperature stability of energy density was achieved. Furthermore, the pulse discharge performance of AgNbO3-based ceramics was evaluated for the first time and a maximum power density of 390 MW/cm3 was obtained in Mn-doped Ag0.97La0.01NbO3 ceramics, which is about 8 times larger than previously reported maximum value (50 MW/cm3). These results reveal Mn-doped Ag0.97La0.01NbO3 ceramics as a good candidate for lead-free high power capacitors.

Introduction Over the past decades, dielectric materials with high energy density have drawn increasing attention for power electronic applications such as electrical vehicles, particle beam accelerator, and electromagnetic weapons, due to their fast charge-discharge capability and high power density.1-3 Among the dielectric materials, antiferroelectric (AFE) materials usually show superior energy storage density comparing to their ferroelectrics (FE) and linear dielectric counterparts.4,5 The neighboring dipoles in AFE material are oriented along opposite directions in its initial state and then align to the same direction once an external electric field is applied, which should be high enough to drive AFE-FE phase transition. During this process, the electrical energy is stored in the AFE material. When the electric field is removed, the FE phase transfers back to the AFE phase, i.e. the aligned neighboring 2 ACS Paragon Plus Environment

Page 3 of 23 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


dipoles reverse to its initial anti-phase orientation, and release the previously stored energy sharply. Energy releasing in such a short time would generate a large power density. Due to the fact that this AFE-FE phase transition sequence is reversible and can be repeated more than thousands of times, the AFE materials have been regarded as preferential candidates for energy storage devices. The most studied AFE materials are lanthanum doped lead zirconate titanate (PLZT)-based ceramics,6-10 with high recoverable energy density Wre up to 6.4 J/cm3 being reported.9 However, the high toxicity of lead-containing compounds increasingly cause detrimental environmental pollution11 and impose us an great urgent to develop lead-free alternative AFE materials for energy storage applications. Recently, AgNbO3 is being investigated as a promising candidate for AFE energy storage materials due to its double polarization-electric field (P-E) hysteresis loops and large saturation polarization of ~50 μC/cm2.12 The Wre of pure AgNbO3 is reported to be 1.6 J/cm3 at 140 kV/cm and 2.1 J/cm3 at 175 kV/cm,13,14 which still can not satisfy the commercial requirement. Studies have found that AgNbO3 shows perovskite structure and belongs to space group of Pmc21 at room temperature.15 With increasing temperature, a series of phase transitions can be observed,34 which is illustrated in Fig.1. For normal AFE structure, cation displacements are antiparallel to each other and they cancel out to show a zero polarization. But for AgNbO3-based ceramics, the structure is ferrielectric,15 where both Ag+ and Nb5+ cations experience antiparallel off-center displacements within their respective polyhedra, whereas the associated dipole moments do not cancel each other completely.14,15 This results in a nonzero remnant polarization Pr after experiencing high electric field, which has a negative impact on the Wre.16 According to the definition of Wre ( Wre 

Pmax



EdP , where E is the applied electric field and Pmax is the maximum polarization), the key

Pr

strategy to increase Wre of AgNbO3-based antiferroelectrics should be enhancing the field-induced-ferroelectric to 3 ACS Paragon Plus Environment


Page 4 of 23

antiferroelectric backward transition field EA and reducing the Pr at the same time. Generally, for perovskite structure there is a Goldschmidt tolerance factor, t  ( RA  RO ) / 2( RB  RO ) , where RA, RB, and RO are the ionic radius of A-site cation, B-site cation and oxygen anion, respectively. The decreased t would lead to the enhancement of antiferroelectricity and thus causes the increment of EA.17 Compared with Ag+ (0.128 nm for eight coordinate), La3+ (0.116 nm for eight coordinate) shows smaller ion radius18 and La can substitute Ag in some extent in the AgNbO3 structure.19 Therefore, it is expected that La would enhance the antiferroelectricity of AgNbO3 and increase the EA. Furthermore, it has been previously reported that Mn can effectively reduce the Pr down to zero.13 Thus the influence of Mn substitution in the Ag0.97La0.01NbO3 structure was also studied to clarify the function of Mn ion and to further enhance the Wre. On the other hand, the actual discharge performance is critical for the power electric applications and only a few studies have focused on the discharge properties of dielectric materials.20-23 For example, Li et al.22 reported that the pulse discharge current waveforms of relaxor-ferroelectric 0.88BaTiO3-0.12Bi(Li0.5Nb0.5)O3 show fast discharge time (less than 0.5 μs) under different electric fields. Xu et al.21 evaluated the discharge properties of Pb0.94La0.04[(Zr0.70Sn0.30)0.90Ti0.10]O3 AFE ceramics and obtained a high peak power density of 50 MW/cm3. Wang et al.23 studied the discharge properties of barium potassium niobate-based glass-ceramics, and found that the discharge efficiency reduced with increasing crystallization temperature due to interfacial polarization. However, as one of the typical lead-free antiferroeletric materials, the discharge performance of AgNbO3-based ceramics has not yet been evaluated in the literatures.

Experimental section Polycrystalline ceramic samples of AgNbO3, Ag0.97La0.01NbO3, 0.3wt% Mn-doped Ag0.97La0.01NbO3 were prepared by conventional solid-state reaction process. The starting materials of Ag2O (99.7%), Nb2O5(99.93%), 4 ACS Paragon Plus Environment

Page 5 of 23 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


La2O3(99.95%), and MnO2(99.95%) were ball-milled in ethanol for 12h. After drying, the mixtures were calcined at 870°C for 2h in O2 atmosphere. The calcined powders were milled again and pressed into disks of 13 mm in diameter and 2 mm in thickness under 200 MPa uniaxial pressure. The disks were subsequently sintered at temperatures of 1050-1100°C for 2h in O2 atmosphere to prevent the decomposition of silver oxide at high temperature. The optimal sintering temperatures were obtained through measuring bulk density of ceramic samples sintered at different temperatures by using Archimedes’ method, as shown in Fig. S1. The grain morphology of the samples was observed using a field emission scanning electron microscope (FESEM, S-4800, Hitachi, Tokyo, Japan). The crystal structure of the samples was studied by an X-ray diffractometer (XRD) using Cu Ka radiation (Shimadzu Corp., Japan). Charge states of Mn were analyzed using an X-band (9.4 GHz) electron paramagnetic resonance (EPR) spectrometer (Bruker EMX spectrometer) at 10 K. Transmission electron microscope (TEM) investigation was performed on a JEM-2100F with double tilting stage, operating at 200 kV. The specimens for TEM analysis were prepared by mechanical thinning and finally Ar+ milling in a Gatan Precision Ion Polishing System. To measure the electric properties, the ceramic samples were polished down to a thickness of 0.15 mm. Silver electrodes were sputtered on the two main surfaces by RF magnetron sputtering method and the electrode is 1.5 mm in diameter. The temperature-dependent dielectric constant on heating and cooling was measured using a broadband dielectric Novocontrol Alpha spectrometer (Novocontrol Technologies, Germany). The polarization-field (P-E) and polarization current-field (I-E) loops were measured with a ferroelectric measurement system at 1 Hz (aixACCT TF Analyzer 1000, Germany). The discharge properties of Mn-doped Ag0.97La0.01NbO3 were investigated with a specially designed, high-speed capacitor discharge circuit, as shown in Fig. S2.

Results and Discussion 5 ACS Paragon Plus Environment


Page 6 of 23

Fig. 2 shows the surface microstructures of AgNbO3, Ag0.97La0.01NbO3, Mn-doped Ag0.97La0.01NbO3 ceramics respectively. It can be seen that all three samples possess dense and homogeneous morphology. And after measurement through Archimedes’ method, it can be calculated that all ceramic samples have theoretical density higher than 95%. In order to further identify the average grain size of the ceramics, the grain size distributions were carried out using an analytical software (Nano Measurer). The statistics results on the grain size distributions are exhibited in the inset of Fig. 2(a)-2(c). It can be seen that the average grain size of pure AgNbO3 is about 4.73 μm. However, Ag0.97La0.01NbO3 shows a smaller average grain size of 3.07 μm due to the refractory nature of La2O3,24 which is also observed in PLZT system.24 After adding 0.3wt% Mn, the average grain size increases to 3.53 μm, since Mn-dopant and the induced oxygen vacancies improve the mobility of grain boundaries and enhance the mass transportation.25,26 Fig. 3 displays the XRD patterns of these three compositions, all of which are assigned to perovskite structure and no second phase can be observed within the limit of XRD. Compared with pure AgNbO3, the (020), (114), (220), and (008) peaks of Ag0.97La0.01NbO3 shift to higher angles, indicating the decreased lattice parameters. This should be attributed to the substitution of Ag+ by La3+ with smaller ion radius, through the solid solution mechanism of A site cation vacancy (as equation 1 shows). AgNbO3 ＇   La 2O3  3 Nb2O5  2 La  Ag  4VAg  6 NbNb  18Oo

(1)

With 0.3wt% Mn addition, the diffraction peaks continue to move to higher angles, which indicates that Mn ions are incorporated into AgNbO3 lattices. Considering the radii of Mn2+ (0.083 nm when CN=6; 0.096 nm when CN=8), Mn3+(0.065 nm when CN=6), Mn4+ (0.053 nm when CN=6), Ag+ (0.128 nm when CN=8) and Nb5+(0.064 nm when CN=6),18 there are two possible solid solution mechanisms for Mn ions: 1) diffusion into B-site as Mn4+; 2) diffusion into A-site as Mn2+/Mn3+/Mn4+. 6 ACS Paragon Plus Environment

Page 7 of 23 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


To further clarify the effect of Mn ion, the detailed charge state of Mn in Mn-doped Ag0.97La0.01NbO3 is studied by EPR measurement, as shown in Fig. 4. A dominant sextet splitting peak around 340 mT is observed. Based on the observed g-value (giso = 2.0175) and the size of the hyperfine splitting (aiso = 245 MHz), the paramagnetic center is attributed to Mn2+.27,28 Since the aiso value of Mn4+ is around 220 MHz,29 the possibility of Mn4+ can be excluded although the samples are sintered in O2 atmosphere. Considering that the microwave quantum of energy is smaller than the splitting between the ground state and the corresponding higher energy levels, the Mn3+ could not be verified within the EPR frequency range (9.4 GHz).30 Nevertheless, it is reported that Mn ions have different valences at different temperatures (as equation 2 shows).31,32 535℃ 1080℃ 1650℃ MnO2   Mn2O3   Mn3O4   MnO

(2)

Since the Mn-doped Ag0.97La0.01NbO3 ceramics are sintered at 1050°C, we can deduce that Mn3+ ion also exist.

Consequently, it is inferred that the coexistence of Mn2+/Mn3+ in the A-site that makes the XRD peaks shift to higher angles, which is consistent with previous report.13 Although there is still possibility of Mn3+ in the B-site, since the combined influence of Mn2+ in A-site and Mn3+ in B-site may also make unit cell smaller and make the XRD peaks shift to higher angles. Fig. 5 shows the temperature dependent real and imaginary parts of dielectric constant on heating and cooling cycle at 1 MHz in pure AgNbO3, Ag0.97La0.01NbO3, and Mn-doped Ag0.97La0.01NbO3 ceramics, respectively. (the temperature dependent dielectric properties under different frequencies from 1kHz to 1MHz can be found in Fig. S3) For pure AgNbO3 on heating, the dielectric constant increases with increasing temperature and two broad local maximum values at 67°C and 267°C are observed. They belong to the (a-,b-,c+)/(a-,b-,c-) octahedral tilting system and correspond to M1-M2, M2-M3 phase transitions, respectively.33,34 A sharp jump at 353°C is associated with the antiferroelectric-paraelectric (M3-O) phase transition. Above this point, the dielectric constant drops as temperature 7 ACS Paragon Plus Environment


Page 8 of 23

increases. On cooling, the M3-O phase transition is accompanied with some degrees of thermal hysteresis, while the thermal hysteresis of M1-M2 and M2-M3 is unnoticeable. Moreover, an extra dielectric anomaly is observed at 179°C, which is virtually undetectable on heating. This is assigned to the freezing temperature Tf, where the antipolar dipoles become frozen as the cations order.33,35 Below Tf there are local polar regions which can expand during electric loading within an average non-polar matrix, whereas, the structure of M2 above Tf is non-polarizable antiferroelectric.33 From the imaginary parts of dielectric constant, the M1-M2 phase transition can also be observed on heating and cooling, although the phase transition temperature is a few degrees lower than that observed upon heating. The freezing temperature Tf, again, only appears during cooling for the imaginary parts, and the temperature equals exactly the value observed from the real parts of dielectric constant curve (179°C), which indicates its second order transition nature.14 As for Ag0.97La0.01NbO3, the temperature dependent dielectric constant keep similar regularities with that of pure AgNbO3. But the dielectric constant value increases after La-doping and all the dielectric anomalies shift to lower temperatures, which is similar with the effect of K ion in AgNbO3.36 And the freezing temperature Tf appears at 150°C. It means that there are still local polar regions for Ag0.97La0.01NbO3, which make this composition incomplete antiferroelectric. After adding 0.3wt% Mn, the dielectric constant value further increases slightly but the dielectric constant curve shows great change. The M3-O phase transition displays a much larger thermal hysteresis and the M1-M2 phase transition is shifted to -5°C. More importantly, the freezing temperature Tf is suppressed instead of shifting to lower temperature as in Ag1-3xBixNbO3 system.33 Even from the imaginary parts of the dielectric constant, Tf could not been observed. This indicates that the local polar region totally disappears, resulting in a stable antiferroelectric phase during a broad temperature range, from -5°C to 247°C. According to Levin’s report,37 Nb5+ are randomly disordered along eight directions in the [NbO6] octahedra at high temperature, although two of them are preferred. On cooling the probabilities for the 8 ACS Paragon Plus Environment

Page 9 of 23 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


remaining six orientations decrease gradually and vanish below Tf, where the Nb5+ cation order into antipolar arrays, resulting in the observed dielectric anomaly at Tf. Hence it is inferred that the coexistence of Mn2+ and Mn3+ in the A-site disrupts the randomly disordered Nb5+ over eight sites, and make the Nb5+ cation order into antipolar arrays at high temperature, thus resulting in the disappearance of Tf.33,37 The various phase transition temperatures for those three compositions are also summarized in Table 1. Besides, it is worth to mention that the dielectric loss for AgNbO3, Ag0.97La0.01NbO3, and Mn-doped Ag0.97La0.01NbO3 under 1kHz is 1%, 1.1% and 0.8% respectively. The Mn-doping effectively makes the dielectric loss decrease and would reduce the heat generated during ceramics’ discharge process.7 Moreover, the low dielectric loss of Mn-doped Ag0.97La0.01NbO3 is superior to other AgNbO3based ceramics13 and even comparable with some lead-containing ceramics7, 8, which is favorable for practical power electronic applications. Table 1. Phase transition temperatures of AgNbO3, Ag0.97La0.01NbO3, Mn-doped Ag0.97La0.01NbO3 ceramics Composition

M1-M2 (°C)

Tf (°C)

M2-M3 (°C)

M3-O (°C)

AgNbO3 Ag0.97La0.01NbO3 Mn-doped Ag0.97La0.01NbO3

67 29 -5

179 150 /

267 247 247

353 341 350

Fig. 6a displays the polarization-electric field (P-E) loop and current-electric field (I-E) loop of pure AgNbO3. Electric field transition from the initial AFE-like to FE state is marked as ±EF, and the backward transition field is marked as ±EA. The difference between EF and EA, ΔE (ΔE= EF -EA) signifies the electric hysteresis. Additionally, two small current peaks (marked as ±EU) are observed at ±37 kV/cm, which are attributed to a polarizable ferrielectric-like structure below Tf.33 The presence of the ±EU peaks indicates that the structure exhibits remnant polarization (3.9 μC/cm2) after high electric field cycling. Furthermore, the recoverable energy density Wre can be calculated to be 2.4 J/cm3, and the energy efficiency η can be calculated to be 41%, according to the definition equation of 3, 4 and 5. 9 ACS Paragon Plus Environment


Wre 

Page 10 of 23

Pmax



EdP

(3)

EdP

(4)

Pr

Wst 

Pmax

 0

  Wre / Wst

(5)

Fig. 6b shows the P-E and I-E loops of Ag0.97La0.01NbO3, it can be seen that EA increases greatly from 52 kV/cm (for pure AgNbO3) to 76 kV/cm, which demonstrates an enhanced AFE stability since the field-induced FE is more readily to reverse to AFE state upon removal of electric field.10 The EU peaks are not so clearly visible but can still be observed at 30 kV/cm. This also indicates the enhancement of AFE stability and suppression of ferrielecrtric structure. As for Mn-doped Ag0.97La0.01NbO3 in Fig. 6c, the EU peaks disappear completely, the remnant polarization Pr is reduced to 1.8 μC/cm2, the EA is further increased to 86 kV/cm and the Pmax is slightly reduced to 39.6 μC/cm2. This means the structure is completely antiferroelectric phase and no local polar region is contained, which is consistent with the dielectric properties shown in Fig. 5. Either enhancing the EA or decreasing the Pr will improve positively the energy storage properties of AN-based ceramics. As a combined effect of La and Mn, the recoverable energy density Wre of Mn-doped Ag0.97La0.01NbO3 reaches a large value of 3.2 J/cm3, which is among the highest values for lead-free ceramics.13,14,16,20,22,33,38-40 The detailed energy storage parameters for those three compositions

are summarized for comparison in Table 2. Table 2. Properties of AgNbO3, Ag0.97La0.01NbO3, Mn-doped Ag0.97La0.01NbO3 ceramics Composition

EF kV/cm

EA kV/cm

ΔE kV/cm

EU kV/cm

Pr μC/cm2

Pmax μC/cm2

Wre J/cm3

η %

AgNbO3 Ag0.97La0.01NbO3 Mn-doped Ag0.97La0.01NbO3

138 142 142

52 76 86

86 66 56

37 30 /

3.9 3.5 1.8

45.4 44.5 39.6

2.4 3.0 3.2

41 51 62

Fig. 7a and 7d show the dark-field TEM morphology of AgNbO3 and Mn-doped Ag0.97La0.01NbO3 ceramics,


Page 11 of 23 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


respectively. It can be observed that the ceramics have higher density of domain wall after La/Mn co-doping. The feature of antiphase boundaries (dark lines marked by yellow arrows) signifies the typical antiferroelectricity of AgNbO3 and Mn-doped Ag0.97La0.01NbO3 ceramics.41 However the (00l) reflections with l = 2n + 1 (003 are marked by red arrow) in Fig. 7c give the evidence of the existence of polar phase with space group Pb21m.14 And the Pb21m polar phase in the nonpolar matrix accounts for the ferrielectric behavior with nonzero Pr at room temperature.16 For the Mn-doped Ag0.97La0.01NbO3 ceramics, the (00l) reflections with l = 2n + 1 become much weaker (shown in Fig. 7f) than those observed in pure AgNbO3, indicating decreased stability of ferrielectric order and thus the enhancement of antiferroelectricity.16 To investigate the temperature stability of Mn-doped Ag0.97La0.01NbO3, the P-E loops were measured at different temperatures and illustrated in Fig. 8a. It can be seen that the hysteresis loops gradually narrow down as the temperature increases, while the area between the polarization axis and the backward switching branch does not change too much, which indicates a good temperature stability of Wre. Fig. 8b shows the regularities of Pr and Pmax with varying temperature. Due to the increasing leakage current at high temperatures (shown in Fig. S4), both Pmax and Pr increase monotonically with increasing temperature, resulting in a relatively unchanged value of Pmax-Pr. Fig. 8c presents the EF and EA as a function of temperature. The EF declines slightly with rising temperature due to the gradually lowered free energy barrier between AFE and field-induced FE, whereas the EA increases with rising temperature since elevated temperature favors the short-range interaction and enhances the stability of AFE phase. The opposite evolution regularities of EF and EA make the electric hysteresis ΔE show decreasing tendency. Fig. 8d further presents the temperature stability of Wre and η. It can be seen that Wre changes from 2.76J/cm3 at 25°C to 3.11 J/cm3 at 145°C, varying less than 1.1% per 10°C. This good thermal stability of Wre could be attributed to the suppression of Tf and the enhanced stability of antiferroelectric M2 phase in the broadened temperature range from 11 ACS Paragon Plus Environment


Page 12 of 23

-5°C to 247°C, as shown in Fig. 5c. Moreover, it is worth to mention that the energy efficiency remains above 60% over the wide temperature range of 25-145°C, which is higher than that reported for other AgNbO3-based antiferroelectric ceramics, such as ANT and ANW.16,38 For practical application, the pulse discharge performance is also critical to evaluate the energy storage material under real working conditions. The discharge current curves of Mn-doped Ag0.97La0.01NbO3 ceramics at different electric fields (E) are presented in Fig. 9a. The current curves all display sinusoidal attenuation waves which indicate underdamp condition of the discharge circuit (shown in Fig. S2). As electric field increases, both peak current Imax and period time t increase. However, there is a large augment for Imax and t when E increases from 142 kV/cm to 150kV/cm, i.e. above the AFE-FE phase transition field. At 150 kV/cm, the peak current is as high as 728A and the period time is 72ns. This phenomenon is associated with the nonlinear dielectric properties of AFE ceramics in discharge circuit. For underdamp circuit ( R  2 L / C ), Imax and t can be expressed as equation 6 and 7, 42

I m ax

t

C arctan 4 L / R 2C  1 C U exp(  ) U 2 L L 4L / R C  1

2 1/ LC  R 2 / 4 L2

 2 LC

(6)

(7)

where U, R, L and C represent the applied voltage, parasitic resistance of the circuit, parasitic inductance of the circuit, and capacitance of the AFE ceramics, respectively. Thus Imax is a function of U and C, and t is proportional to the square root of C. When E is below EF, the capacitance of the AFE ceramics only increases slightly with increasing E, which results in a slight increase of t. The Imax shows more obvious increment since Imax is also directly proportional to U. However, when E approaches to EF, the capacitance of AFE ceramics increases sharply due to the AFE-FE phase transition. Therefore, both Imax and t show abrupt augments. During the discharge process, the voltage of the ceramic sample can be detected by a voltage probe. Thus the 12 ACS Paragon Plus Environment

Page 13 of 23 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


voltage-time (U-t) waveform or electric field-time (E-t) waveform upon discharging could be obtained. The E-t waveform at 150 kV/cm is shown in the inset of Fig. 9a. It describes the change of electric field across the Mndoped Ag0.97La0.01NbO3 ceramic sample with time during discharging process: drops rapidly from 150 kV/cm to 20 kV/cm at the beginning and then gradually attenuates to zero as a function of cosine waveform. Combine the current curve and electric field curve at 150 kV/cm together, the power density p can be calculated as equation 8,

p (t ) 

U (t ) I (t ) E (t ) I (t )  V S

(8)

where V and S represent the volume and surface area of the ceramic sample respectively. Fig. 9b displays the calculated power density p as a function of time. A sharp peak with bottom width of 51 ns is observed and the power density reaches as high as 390 MW/cm3 within less than 30 ns. This is inevitable for ceramics’ possible pulse power applications: a large power density need to be generated within an extremely short time span. Fig. 10 compare the energy density Wre and maximum power density pmax of Mn-doped Ag0.97La0.01NbO3 with other lead-containing and lead-free ceramics reported previously.5,7,20,21,24,43-47 It can be seen that Mn-doped Ag0.97La0.01NbO3 ceramics possesses a large Wre of 3.2 J/cm3, and can generate a giant pmax of 390 MW/cm3 at 150 kV/cm. Note that the power density reported here is almost 8 times higher than the largest value in previous reports (50 MW/cm3).21 By utilizing the approximate calculating equation of pmax (equation 9) 7,

pmax 

EI max 2S

(9)

the reasons for this large power density can be analyzed. Firstly, the working electric field of 150 kV/cm is much larger than that of PLZST antiferroelectric ceramics (82 kV/cm for Pb0.98La0.02(Zr0.35Sn0.55Ti0.10)0.995O3,7 for example). This is one advantage of AgNbO3-based antiferroelectric ceramics, i.e. a relatively high AFE-FE phase transition field and working electric field. Moreover, this working field could be further improved after increasing 13 ACS Paragon Plus Environment


Page 14 of 23

the breakdown strength through glass-aided sintering, hot-press sintering, and spark plasma sintering, which can be effective to further improve the power density.9 Secondly, the current density Imax/S reaches as high as 4022 A/cm2. This is the largest current density that currently could be obtained in AFE ceramics and is about 9 times higher than our former result (438A/cm2).7 Considering equation 10,

I m ax dQmax dPmax   S Sdt dt

(10)

the large current density should be attributed to the large polarization of Mn-doped Ag0.97La0.01NbO3. Although Ag does not have lone-pair electrons like Pb, theoretical investigations suggest that there is hybridization between Ag and O in AgNbO3,48,49 resulting in a large off-center displacement in the A-site.49 This may account for the large polarization in AgNbO3-based ceramics, which means more charges could be released during discharge process. This is another advantage of AgNbO3-based ceramics for power electronic application, i.e. a large value of polarization.

Conclusions In summary, through La/Mn co-doping in AgNbO3 ceramics, a large energy density of 3.2 J/cm3 was achieved, which is among the highest ones in lead-free ceramics. La was found to enhance the ferroelectric-antiferroelectric backward phase transition field EA and thus the stability of the AFE phase. Mn was diffused into the A-site as Mn2+/Mn3+, which disrupts the randomly disordered Nb5+ at high temperature, leading to the disappearance of freezing temperature Tf and thus the enhancement of antiferroelectric stability, too. As a result, the antiferroelectric M2 phase was stable over a broad temperature range (-5°C~247°C) and a good temperature stability of Wre was obtained: varying less than 1.1% per 10°C from 25°C to 145°C. Furthermore, the pulse discharge performance of AgNbO3-based ceramics was investigated for the first time and a maximum power density of 390 MW/cm3 was 14 ACS Paragon Plus Environment

Page 15 of 23 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


achieved in Mn-doped Ag0.97La0.01NbO3 ceramics, which is about 8 times larger than previously reported maximum value (50 MW/cm3 for Pb0.94La0.04[(Zr0.70Sn0.30)0.90Ti0.10]O3 ceramics21). This large power density reveals two advantages of AgNbO3-based AFE ceramics for power electronic applications: a relatively high AFE-FE phase transition field and a large saturation polarization.

ASSOCIATED CONTENT Supporting Information This material is available free of charge via the Internet at http://pubs.acs.org. Schematic diagram of the discharge measuring system. Temperature dependent dielectric properties of pure AgNbO3, Ag0.97La0.01NbO3, and Mn-doped Ag0.97La0.01NbO3 ceramics under frequencies from 1 kHz to 1 MHz. Leakage current density of Mn-doped Ag0.97La0.01NbO3 ceramics as a function of electric field with increasing temperature.

AUTHOR INFORMATION Corresponding authors *E-mail: [email protected] Notes: The authors declare no competing financial interest.

Acknowledgements This work was supported by the National Natural Science Foundation of China (No.11774366). Zhen Liu also 15 ACS Paragon Plus Environment


Page 16 of 23

acknowledges the support of Shanghai Sailing Program (No. 17YF1429700). A portion of this work was performed on the Steady High Magnetic Field Facilities, High Magnetic Field Laboratory, CAS.

References (1) Yao, Z.; Song, Z.; Hao, H.; Yu, Z.; Cao, M.; Zhang, S.; Lanagan, M. T.; Liu, H., Homogeneous/InhomogeneousStructured Dielectrics and their Energy-Storage Performances. Adv. Mater. 2017, 29, 1601727. (2) Jo, H. R.; Lynch, C. S. A high energy density relaxor antiferroelectric pulsed capacitor dielectric. J. Appl. Phys. 2016, 119, 024104. (3) Chu, B.; Zhou, X.; Ren, K.; Neese, B.; Lin, M.; Wang, Q.; Bauer, F.; Zhang, Q. A dielectric polymer with high electric energy density and fast discharge speed. Science 2006, 313, 334-336. (4) Hao, X.; Zhai, J.; Kong, L. B.; Xu, Z., A comprehensive review on the progress of lead zirconate-based antiferroelectric materials. Prog. Mater. Sci. 2014, 63, 1-57. (5) Zhang, H.; Chen, X.; Cao, F.; Wang, G.; Dong, X.; Hu, Z.; Du, T., Charge–Discharge Properties of an Antiferroelectric Ceramics Capacitor Under Different Electric Fields. J. Am. Ceram. Soc. 2010, 93, 4015-4017. (6) Zhang, Q.; Tong, H.; Chen, J.; Lu, Y.; Yang, T.; Yao, X.; He, Y. High recoverable energy density over a wide temperature range in Sr modified (Pb,La)(Zr,Sn,Ti)O3 antiferroelectric ceramics with an orthorhombic phase. Appl. Phys. Lett. 2016, 109, 262901. (7) Xu, C.; Liu, Z.; Chen, X.; Yan, S.; Cao, F.; Dong, X.; Wang, G. High charge-discharge performance of Pb0.98La0.02(Zr0.35Sn0.55Ti0.10)0.995O3 antiferroelectric ceramics. J. Appl. Phys. 2016, 120, 074107. (8) Wang, X.; Yang, T.; Shen, J. High-Energy Storage Performance in (Pb0.98La0.02)(Zr0.45Sn0.55)0.995O3 AFE Thick Films Fabricated via a Rolling Process. J. Am. Ceram. Soc. 2016, 99, 3569-3572. (9) Zhang, L.; Jiang, S.; Fan, B.; Zhang, G. Enhanced energy storage performance in (Pb0.858Ba0.1La0.02Y0.008)(Zr0.65Sn0.3Ti0.05)O3–(Pb0.97La0.02)(Zr0.9Sn0.05Ti0.05)O3 anti-ferroelectric composite ceramics by Spark Plasma Sintering. J. Alloys Comp. 2015, 622, 162-165. (10) Liu, Z.; Chen, X.; Peng, W.; Xu, C.; Dong, X.; Cao, F.; Wang, G., Temperature-dependent stability of energy storage properties of Pb0.97La0.02(Zr0.58Sn0.335Ti0.085)O3 antiferroelectric ceramics for pulse power capacitors. Appl. Phys. Lett. 2015, 106, 262901. (11) Hong, C. H.; Kim, H. P.; Choi, B. Y.; Han, H. S.; Son, J. S.; Ahn, C. W.; Jo, W., Lead-free piezoceramics – Where to move on? J. Materiomics 2016, 2, 1-24. (12) Fu, D.; Endo, M.; Taniguchi, H.; Taniyama, T.; Itoh, M. AgNbO3: A lead-free material with large polarization and electromechanical response. Appl. Phys. Lett. 2007, 90, 252907. (13) Zhao, L.; Liu, Q.; Zhang, S.; Li, J. F. Lead-free AgNbO3 anti-ferroelectric ceramics with an enhanced energy storage performance using MnO2 modification. J. Mater. Chem. C 2016, 4, 8380-8384. (14) Tian, Y.; Jin, L.; Zhang, H.; Xu, Z.; Wei, X.; Politova, E. D.; Stefanovich, S. Y.; Tarakina, N. V.; Abrahams, I.; Yan, H. High energy density in silver niobate ceramics. J. Mater. Chem. A 2016, 4, 17279-17287. (15) Yashima, M.; Matsuyama, S.; Sano, R.; Itoh, M.; Tsuda, K.; Fu, D. Structure of Ferroelectric Silver Niobate AgNbO3. Chem. Mater. 2011, 23, 1643-1645. (16) Zhao, L.; Liu, Q.; Gao, J.; Zhang, S.; Li, J. F. Lead-Free Antiferroelectric Silver Niobate Tantalate with High Energy Storage Performance. Adv. Mater. 2017, 29, 1701824. (17) Shimizu, H.; Guo, H.; Reyes-Lillo, S. E.; Mizuno, Y.; Rabe, K. M.; Randall, C. A. Lead-free antiferroelectric: 16 ACS Paragon Plus Environment

Page 17 of 23 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


xCaZrO3-(1-x)NaNbO3 system (0≤x≤0.10). Dalton Trans. 2015, 44, 10763-10772. (18) Shannon, R. D. Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. Acta Crystallogr. 1976, 32, 751-767. (19) Li, G.; Kako, T.; Wang, D.; Zou, Z.; Ye, J. Enhanced photocatalytic activity of La-doped AgNbO3 under visible light irradiation. Dalton Trans. 2009, 2423-2427. (20) Yuan, Q.; Yao, F.; Wang, Y.; Ma, R.; Wang, H. Relaxor ferroelectric 0.9BaTiO3-0.1Bi(Zn0.5Zr0.5)O3 ceramic capacitors with high energy density and temperature stable energy storage properties. J. Mater. Chem. C 2017, 5, 9552-9558. (21) Xu, R.; Li, B.; Tian, J.; Xu, Z.; Feng, Y.; Wei, X.; Huang, D.; Yang, L. Pb0.94La0.04[(Zr0.70Sn0.30)0.90Ti0.10]O3 antiferroelectric bulk ceramics for pulsed capacitors with high energy and power density. Appl. Phys. Lett. 2017, 110, 142904. (22) Luo, B.; Wang, X.; Tian, E.; Song, H.; Wang, H.; Li, L. Enhanced Energy-Storage Density and High Efficiency of Lead-Free CaTiO3-BiScO3 Linear Dielectric Ceramics. ACS Appl. Mater. Interfaces 2017, 9, 19963-19972. (23) Wang, H.; Liu, J.; Zhai, J.; Shen, B. Ultra High Energy-Storage Density in the Barium Potassium NiobateBased Glass-Ceramics for Energy-Storage Applications. J. Am. Ceram. Soc. 2016, 99, 2909-2912. (24) Xu, R.; Tian, J.; Zhu, Q.; Zhao, T.; Feng, Y.; Wei, X.; Xu, Z. Effects of La-induced phase transition on energy storage and discharge properties of PLZST ferroelectric/antiferroelectric ceramics. Ceram. Int. 2017, 43, 1391813923. (25) Peng, P.; Nie, H.; Liu, Z.; Ren, W.; Cao, F.; Wang, G.; Dong, X. Enhanced ferroelectric properties and thermal stability of Mn-doped 0.96(Bi0.5Na0.5)TiO3-0.04BiAlO3 ceramics. J. Am. Ceram. Soc. 2017, 100, 1030-1036. (26) Liu, Q.; Zhu, F. Y.; Zhao, L.; Wang, K.; Li, L.; Li, J. F. Further Enhancing Piezoelectric Properties by Adding MnO2 in AgSbO3-Modified (Li,K,Na)(Nb,Ta)O3 Lead-Free Piezoceramics. J. Am. Ceram. Soc. 2016, 99, 36703676. (27) Aksel, E.; Jakes, P.; Erdem, E.; Smyth, D. M.; Ozarowski, A.; van Tol, J.; Jones, J. L.; Eichel, R. A. Processing of Manganese-Doped [Bi0.5Na0.5]TiO3 Ferroelectrics: Reduction and Oxidation Reactions During Calcination and Sintering. J. Am. Ceram. Soc. 2011, 94, 1363-1367. (28) Wang, L.; Zhou, Z.; Zhao, X.; Liu, Z.; Liang, R.; Dong, X. Enhanced strain effect of aged acceptor-doped BaTiO3 ceramics with clamping domain structures. Appl. Phys. Lett. 2017, 110, 102904. (29) Eichel, R. A. Defect structure of oxide ferroelectrics-valence state, site of incorporation, mechanisms of charge compensation and internal bias fields. J. Electroceram. 2007, 19, 11-23. (30) Drahus, M. D.; Jakes, P.; Erdem, E.; Schaab, S.; Chen, J.; Ozerov, M.; Zvyagin, S.; Eichel, R. A. Manganesedoped (1− x) BiScO3–x PbTiO3 high-temperature ferroelectrics: Defect structure and mechanism of enhanced electric resistivity. Phys. Rev. B 2011, 84, 064113. (31) Du, G.; Liang, R.; Wang, L.; Li, K.; Zhang, W.; Wang, G.; Dong, X. Large stable strain memory effect in poled Mn-doped Pb(Mn1/3Sb2/3)O3-Pb(Zr,Ti)O3 ceramics. Appl. Phys. Lett. 2013, 102, 162907. (32) Ng, Y. S.; Alexander, S. M. Structural studies of manganese stabilised lead-zirconate-titanate. Ferroelectrics 1983, 51, 81-86. (33) Tian, Y.; Jin, L.; Zhang, H.; Xu, Z.; Wei, X.; Viola, G.; Abrahams, I.; Yan, H. Phase transitions in bismuthmodified silver niobate ceramics for high power energy storage. J. Mater. Chem. A 2017, 5, 17525-17531. (34) Ph, S.; Kania, A.; Dkhil, B.; Suard, E.; Ratuszna, A. Structural investigation of AgNbO3 phases using x-ray and neutron diffraction. J. Phys.: Condens. Matter 2004, 16, 2795. (35) Kania, A.; Kwapulinski, J. Ag(1-x)NaxNbO3 (ANN) solid solutions: from disordered antiferroelectric AgNbO3 17 ACS Paragon Plus Environment


Page 18 of 23

to normal antiferroelectric NaNbO3. J. Phys.: Condens. Matter 1999, 11, 8933. (36) Xu, Y. H.; Wang, G. D.; Tian, Y.; Yan, Y. X.; Liu, X. L.; Feng, Y. J. Crystal structure and electrical properties of AgNbO3-based lead-free ceramics. Ceram. Int. 2016, 42, 18791. (37) Levin, I.; Krayzman, V.; Woicik, J. C.; Karapetrova, J.; Proffen, T.; Tucker, M. G.; Reaney, I. M. Structural changes underlying the diffuse dielectric response in AgNbO3. Phys. Rev. B 2009, 79, 104113. (38) Zhao, L.; Gao, J.; Liu, Q.; Zhang, S.; Li, J. F. Silver Niobate Lead-Free Antiferroelectric Ceramics: Enhancing Energy Storage Density by B-Site Doping. ACS Appl. Mater. Interfaces 2018, 10, 819-826. (39) Yang, H.; Yan, F.; Lin, Y.; Wang, T. Novel Strontium Titanate-Based Lead-Free Ceramics for High-Energy Storage Applications. ACS Sustain. Chem. Eng. 2017, 5, 10215-10222. (40) Yan, F.; Yang, H.; Lin, Y.; Wang, T. Dielectric and Ferroelectric Properties of SrTiO3–Bi0.5Na0.5TiO3– BaAl0.5Nb0.5O3 Lead-Free Ceramics for High-Energy-Storage Applications. Inorg. Chem. 2017, 56, 13510-13516. (41) Wei, X. K.; Tagantsev, A. K.; Kvasov, A.; Roleder, K.; Jia, C. L.; Setter, N. Ferroelectric translational antiphase boundaries in nonpolar materials. Nat. Commun. 2014, 5, 3031. (42) Xu, C.; Liu, Z.; Chen, X.; Yan, S.; Cao, F.; Dong, X.; Wang, G. Pulse discharge properties of PLZST antiferroelectric ceramics compared with ferroelectric and linear dielectrics. AIP Adv. 2017, 7, 115108. (43) Xu, R.; Tian, J.; Zhu, Q.; Feng, Y.; Wei, X.; Xu, Z. Effect of temperature-driven phase transition on energystorage and release properties of Pb0.97La0.02[Zr0.55Sn0.30Ti0.15]O3 ceramics. J. Appl. Phys. 2017, 122, 024104. (44) Li, F.; Yang, K.; Liu, X.; Zou, J.; Zhai, J.; Shen, B.; Li, P.; Shen, J.; Liu, B.; Chen, P. Temperature induced high charge-ischarge performances in lead-free Bi0.5Na0.5TiO3-based ergodic relaxor ferroelectric ceramics. Scripta Mater. 2017, 141, 15-19. (45) Xu, R.; Xu, Z.; Feng, Y.; He, H.; Tian, J.; Huang, D. Temperature Dependence of Energy Storage in Pb0.90La0.04Ba0.04[(Zr0.7Sn0.3)0.88Ti0.12]O3 Antiferroelectric Ceramics. J. Am. Ceram. Soc. 2016, 99, 2984-2988. (46) Chen, X.; Zhang, H.; Cao, F.; Wang, G.; Dong, X.; Gu, Y.; He, H.; Liu, Y. Charge-discharge properties of lead zirconate stannate titanate ceramics. J. Appl. Phys. 2009, 106, 034105. (47) Xu, R.; Tian, J.; Zhu, Q.; Zhao, T.; Feng, Y.; Wei, X.; Xu, Z. Effects of phase transition on discharge properties of PLZST antiferroelectric ceramics. J. Am. Ceram. Soc. 2017, 100, 3618-3625. (48) Yashima, M.; Matsuyama, S. Origin of the Ferrielectricty and Visible-Light Photocatalytic Activity of Silver Niobate AgNbO3. J. Phys. Chem. C 2012, 116, 24902-24906. (49) Grinberg, I.; Rappe, A. M. Silver solid solution piezoelectrics. Appl. Phys. Lett. 2004, 85, 1760-1762.

Figure 1. Phase transition sequence for AgNbO3 ceramics with increasing temperature.


Page 19 of 23 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 2. SEM images of (a) AgNbO3; (b) Ag0.97La0.01NbO3; (c) Mn-doped Ag0.97La0.01NbO3 ceramics respectively.

Figure 3. XRD of AgNbO3, Ag0.97La0.01NbO3, Mn-doped Ag0.97La0.01NbO3 ceramics respectively.

Figure 4. X-band EPR spectra of Mn-doped Ag0.97La0.01NbO3 ceramics at 10 K.



Page 20 of 23

Figure 5. Temperature dependence of real (εr’) and imaginary (εr’’) parts of dielectric constant in (a), (b) AgNbO3 (c), (d) Ag0.97La0.01NbO3 and (e), (f) Mn-doped Ag0.97La0.01NbO3 ceramics respectively.

Figure 6. (a) P-E, and I-E loops of AgNbO3. (b) P-E and I-E loops of Ag0.97La0.01NbO3. (c) P-E, and I-E loops of Mndoped Ag0.97La0.01NbO3.


Page 21 of 23 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 7. TEM characterization of AgNbO3 and Mn-doped Ag0.97La0.01NbO3 ceramics. (a) and (d) are Dark-field images using the (001) reflections of AgNbO3 and Mn-doped Ag0.97La0.01NbO3 ceramics respectively. The dark lines marked by yellow arrows are antiphase boundaries. (b) and (c) are high-resolution electron microscopy (HREM) image and selectedarea electron diffraction (SAED) pattern of domain boundary area in (a) respectively. (e) and (f) are HREM image and SAED pattern of domain boundary area in (d) respectively. Note the crystallographic directions and planes in SAED patterns refer to a single domain.



Page 22 of 23

Figure 8. (a) P-E loops (b) Pr, Pmax, Pmax-Pr (c) EF, EA, EF-EA and (d) Wre, η of Mn-doped Ag0.97La0.01NbO3 ceramics at 25-145°C.

Figure 9. (a) Discharge current curves of Mn-doped Ag0.97La0.01NbO3 ceramics at different electric fields and the inset shows the electric field waveform at 150 kV/cm. (b) Power density p as a function of time.

Figure 10. A comparison of energy density Wre and maximum power density pmax for lead-based and lead-free ceramics.


Page 23 of 23 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


TOC graphic page For Table of Contents Use Only.

Synopsis: Large energy density and power density achieved in environmental-friendly La/Mn co-doped AgNbO3 ceramics for energy storage engineering


Mn Codoped AgNbO3 Lead-Free Antiferroelectric Ceramics with

Recommend Documents