Fabrication of Large Aspect Ratio Ba0.85Ca0.15Zr0.1Ti0.9O3

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Fabrication of Large Aspect Ratio Ba0.85Ca0.15Zr0.1Ti0.9O3 Superfine Fibers Based Flexible Nanogenerator Device: Synergistic Effect on Curie Temperature, Harvested Voltage and Power K Suresh Chary, Himanshu Sekhar Panda, and C Durga Prasad Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.7b02182 • Publication Date (Web): 28 Aug 2017 Downloaded from http://pubs.acs.org on September 3, 2017

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Industrial & Engineering Chemistry Research

Fabrication of Large Aspect Ratio Ba0.85Ca0.15Zr0.1Ti0.9O3 Superfine Fibers Based Flexible Nanogenerator Device: Synergistic effect on Curie Temperature, Harvested Voltage and Power Kammari Suresh Charya, Himanshu Sekhar Pandab*, Chadalapaka Durga Prasada* a b

Naval Materials Research Laboratory, Thane 421506, India`

Department of Materials Engineering, Defence Institute of Advanced Technology, Pune 411025, India

*Corresponding Author Address: b

Dr Himanshu Sekhar Panda

Tel. No.: +91-20-24304205, Email: [email protected], [email protected] Department of Materials Engineering, Defence Institute of Advanced Technology, Girinagar, Pune 411025, India a

Dr C Durga Prasad,

Tel. No.: +91-251-2623168, Fax No.: +91-251-2623004 Email: [email protected] Naval Material Research Laboratory, Thane 421506, India

ACS Paragon Plus Environment


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ABSTRACT:

Large aspect ratio Ba0.85Ca0.15Zr0.1Ti0.9O3 nanofibers mat was prepared using electro-spinning technique. Crystal structure analysis confirmed the existence of MPB between tetragonal and rhombohedra phases. Morphology study suggested the formation of discrete nanofibers having diameter 80-250 nm. Dielectric studies were performed on sintered nanofibers and Curie temperature (Tc) was measured ~108 °C, which showed a significantly improved Tc than bulk BCZT particles. The sintered fibers mat was used for fabricating a flexible nanogenerator using room temperature vulcanized silicone elastomer. The open circuit peak voltage was measured ranging from 5.0-17.5 V. Peak voltage and power output were found ~2.68 V and ~2.95 µW respectively under periodic tapping. Developed BCZT nanofibers mat based nanogenerator may bring into play in wireless microelectronics, energy harvesting device and self-powered sensor for structural health monitoring applications.

Keywords: Electro-spinning, Nanofibers, Nanogenerator, Curie temperature, and Screen printing


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1. INTRODUCTION Piezoelectric ceramics are used in niche areas, such as sensors, actuators, electronics and nonvolatile ferroelectric memory and transistor devices.1-4 Lead zirconate titanate (PZT) is one of the extensively used ceramic due to superior piezoelectric properties.5 However, high lead content in PZT creates environmental pollution during preparation, processing and even disposal. Hence, lead free piezoelectric materials having piezoelectric coefficient comparable to that of PZT (200-700 pC/N) are desired for the development of high performance nanodevices.6-7 Recently, higher piezoelectric coefficients are achieved in lead free ceramics, such as (Na,K)NbO3, BaFeO3 and bismuth sodium titanate by modifying composition. Also, Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) has been appeared as promising lead free piezoceramic having high piezoelectric coefficient (400-650 pC/N) and used for low temperature device application.8-10 Piezoelectric properties enhance in lead free ceramic systems due to phase transition boundary between two ferroelectric phases or even one ferroelectric phase and one non-ferroelectric phase, which is similar to morphotropic phase boundary (MPB) in PZT ceramic.11-14 Further, Hao et al. observed strong dependence of piezoelectric properties on grain size.15 In another aspect, one dimensional (1D) nanomaterials, such as wires, rods, tubes and fibers, are used for fabricating flexible sensors and actuators. Zinc oxide, cadmium sulphide and barium titanate nanowire are employed for converting mechanical energy to electrical energy.16 Piezo-ceramic fibers exhibited extremely high piezoelectric voltage constant, bending flexibility and mechanical strength due to ultra-fine diameter and outsize length. These 1D nanostructures were synthesised by using various techniques, such as phase separation, electrophoretic deposition, template synthesis and electro-spinning.17-18 Electrospinning is a powerful technique to synthesize long and uniform nanofibers/nanotubes. In electro-spinning, formation of nanofibers accomplish through uniaxial stretching of



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viscoelastic gel, which induces through electrostatic force.29,30 Recently, various ceramic nanofibers, such as PMN-PT,19-20 PZT,21-22 BaTiO3,23 BaZr0.1Ti0.9O3,24 YSZ,25 alumina,26 BiFeO3,27 BaxSr1−xTiO328 and Bi3.15Nd0.85Ti3O1229 are synthesized by using sol-gel and electro-spinning process. Chen et al. fabricated PZT fibers based nanogenerator using electrospinning process and generated maximum voltage 1.63 V and power 0.03 µW by tapping through teflon bar on the nanogenerator.19 Wu et al. synthesized 0.5BCT-0.5BZT nanowires and fabricated a nanogenerator having output voltage 3.25 V and current 55 nA.12 Also, Mn doped (NaK)NbO3–PET nanofibers based flexible nanogenerator was generated voltage 0.3 V and output current 50 nA under bending strain.30 However, all the above investigations deal with cumbersome process having high fabrication cost for developing a nanogenerator. Again, there is no report on BCZT nanofibers, though it exhibits high piezoelectric coefficient. Therefore, we hypothesize to fabricate a BCZT nanofibers mat by using a rapid and low cost process and exercise for developing a flexible nanogenerator. In this article, we report a process to fabricate large aspect ratio lead free BCZTpolymer green nanofibers mat by using electro-spinning technique. Binder removal and sintering schedule were standardized for achieving uniform and compact nanofibers (aspect ratio ranging from 2-5 x 105). Green BCZT-PVP and sintered BCZT nanofibers are analysed using various analytical techniques. Dielectric properties of sintered nanofibers mat were measured at different frequencies and temperatures, and results confirmed the enhancement (~23 °C) of Curie temperature (Tc) than bulk BCZT particles. Efforts are made for developing a flexible nanogenerator, and peak voltage and power output are achieved ~2.68 V and ~2.95 µW respectively. 2. EXPERIMENTAL


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2.1. Preparation of ceramic precursor gel. Barium acetate ( 99% Alfa Aeser), calcium acetate hydrate (99% Alfa Aeser), zirconium(IV)acetylacetone (99% Sigma Aldrich), titanium isobutaoxide (Alfa Aeser), acetylacetone (AR grade SRL), acetic acid (AR grade SRL) and polyvinyl pyrrolidine (PVP) (average molecular weight ̴1300000 Sigma Aldrich) were used for preparing BCZT gel. Ti-isobutoxide was modified by reacting with pure acetylacetone (molar ratio- 1:2) for controlling hydrolysis and condensation reaction. 0.85 mole of barium acetate and 0.15 mole of calcium acetate were dissolved in acetic acid, and transferred to a round bottom flask having 0.9 mole of modified Ti-isobutoxide and 0.1 mole of zirconium acetyl acetate in ethanol. Solution was stirred by using a magnetic stirrer at temperature 50-60 °C for 8 h, which formed deep yellow colour solution. 10% (wt/wt) polyvinyl pyrrolidine was added in the above organo-metallic solution for controlling viscosity of ceramic precursor gel. 2.2. Electro-spinning of BCZT-PVP precursor gel. The electro-spinning of BCZT-PVP gel was carried out using MECC NANON- 10A electro-spinning set up. Ceramic precursor gel was taken in a 2.5 ml syringe having 22G (0.794 mm U.S.G) metallic needle and ᴓ100 mm drum collector. The drum collector was covered with an aluminium foil and kept at 100 mm distance from the tip of the syringe. Spinning of BCZT ceramic precursor gel was performed at feed rate 0.2 ml/h with DC voltage 17 kV (E = 0.17 kV/mm) between collector and syringe. Spun green fibers were dried by using a chamber (humidity: 30-35% and temperature: 27 °C). Spun green fibers were peeled out from the aluminium foil and laid on a porous sintered alumina tile. Volatile organic materials were removed by heating at 500 °C for 2 h (ramp rate 1 °C/min). After that, developed fibers were sintered at 700 °C for 3-5 h (ramp rate 2 °C/min). 2.3. Fabrication of flexible nanogenerator. Sintered BCZT nanofibers mat (width (W)- 10 mm, length (L)- 15 mm and thickness (T)- 0.01 mm) and RTV silicon elastomer



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(ELASOSIL-M4511) were used for fabricating a nanogenerator.12 A glass plate was cleaned with deionised water and acetone for removing foreign particles. Thin (40-50 µm) film of silicon elastomer having curing agent was casted on the above glass plate using a doctor blade and pre-cured at room temperature for 2 h. Developed sintered BCZT nanofibers were attached tightly with the above substrate and allowed to cure for 24 h. After curing, interdigited electroding (IDE) was carried out with conducting silver epoxy paste using screen printing technique. The electrodes were connected using copper wires and silver paste. The silicon elastomer and curing agent were mixed to form another top layer for packing the device. The final dimension of the device is 15 mm (W) x 20 mm (L) x 0.5 mm (T). Poling of the device was carried out by applying electric field (0.65 kV/mm) at 40 °C for 150 min.31 Schematic representation of BCZT-based nanogenerator is shown in Figure 1. 2.4 Characterization. Crystal structure and single phase formation of BCZT nanofibers were established through powder X-ray diffractometer (BRUKER D8 ADVANCE) with CuKα radiation (λ = 1.542 Å) with scanning angle (2ϴ range 20-70o). Raman study of developed nanofibers was carried out using Raman spectroscopy (Lab RAM HR (800), HORIBA Scientific with Olympus BX41) having solid state laser excitation wavelength 632 nm. Thermo gravimetric analysis (TGA) of green nanofibers was carried out using TGAQ500 (TA Instrument, Inc., USA) analyser from ambient temperature to 800 °C. Bonding behaviour of BCZT fibers was analysed using fourier transform infrared (FT-IR) spectroscopy (Thermo electron corporation Nicolet 6700). The morphology of green and sintered BCZT nanofibers was obtained using field emission scanning electron microscope (Zeissa Supra 40VP, Germany) and high resolution transmission electron microscope (FEI Tecnai G230, Hillsboro, USA). Elemental analysis and mapping of sintered BCZT fibers are carried out using energy dispersive X-ray analysis (EDX), which is an attachment to the above SEM. Broadband dielectric spectroscopy (BDS) study of nanofibers were performed to


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measure the dielectric permittivity using a Novocontrol broadband dielectric spectrometer with Alpha-A analyser, which is interfaced to the sample cell and equipped with temperature controller. The measurements were carried out in the frequency range 0.1-10 x 106 Hz and temperature range 0–200

o

C. The performance of the developed nanogenerator was

investigated using an oscilloscope (Tektronix TDS 3054C) and recorded output voltage in both tapping and bending modes. The current output was measured across load resistant of 1 MΩ. 3. RESULTS AND DISCUSSION 3.1. Structural investigation of BCZT nanofibers. XRD patterns of nanofibers showed amorphous nature up to sintering temperature 400 °C (Figure 2a). However, XRD pattern indicated the formation of BCZT phase with few percentage of secondary phase (BaCO3) at sintering temperature 500 °C, which is confirmed from the two theta peak at 27°. Again, secondary phase disappeared with further increase in sintering temperature.32 Perovskite phase is appeared above 500 °C and narrowing of the peaks are observed due to grain growth. The crystal structure of pure Ba(Zr0.1Ti0.9)O3 is rhombohedral at room temperature.33 However, Ca+2 ion substitution at ‘A’ site of crystal splitted (002) plane, and indicated the existence of MPB between tetragonal and rhombohedral phases. Lattice parameters ‘a’ and ‘c’ of sintered ceramic calculated (Table 1) around 0.1 Å, which is less than bulk BCZT particles as reported by Shukai et al.34 But, the obtained c/a ratio is 1.004, which is equal to that of bulk ceramic for this composition. The inter-planar distance of (101) plane was calculated around 0.415 nm, which is further supported by HRTEM. The crystallite size was calculated from XRD data using Scherer formula and average crystallite size was calculated around 11.5 nm and 12.7 nm for fibers sintered at 600 °C and 700 °C respectively, which is three times less than bulk ceramic powder.46 Also, crystallite size of developed BCZT nanofibers is 50% less than BCT-BZT nanofibers.12 The Raman spectra of BCZT nanofibers



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was carried out at room temperature for evaluating phases and shown in Figure 2b. The peak at 305 cm-1 attributes to B1 mode of E9TO2 for BCZT and suggests asymmetricity of TiO6 octahedra. The broadening of the A1(TO2) peak at 205 cm-1 represented the phase transformation from tetragonal state to rhombohedral state, and induced

due to Zr

substitution at Ti site.12-14 Also, the peak is appeared at 738 cm-1 due to the tetragonal phase of BCZT, which is associated to the highest longitudinal optical mode of A1(LO) and E (LO) symmetries.42 Also, the above phase formation is supported by TGA. Figure 3a represents the TGA of green and sintered nanofibers. In green nanofibers, the weight loss occurred from ambient temperature to 200 oC due to loss of solvents and moisture. Significant weight loss observed at temperature ranging from 200-280 °C due to decomposition of organic materials and formation of intermediate oxides by losing carbon dioxide and water molecules. Small amount of weight loss occurred at temperature ranging from 280-420 °C due to burning of residual carbon. Formation of ceramic crystals occurred at temperature ranging from 420-650 °C, and supported the XRD results. In order to corroborate, FT-IR study is carried out for green and sintered nanofibers and shown in Figure 3b. As-spun nanofibers mat exhibited more absorption peaks between 600-1600 cm-1 and 2000-3000 cm-1, which indicated the presence of organo-metallic compounds and residual solvents. However, the peaks due to organic functional group are disappeared in the nanofibers after sintering above 500 oC. BCZT fibers (sintered at 700 oC) showed peak at 3452 cm-1 due to the stretching vibration of O-H group. Also, peaks appeared at 664 cm-1 and 733 cm-1 due to the stretching vibration of M-O bonds.35-36 3.2. Morphology study. SEM images of green and sintered nanofibers are shown in Figure 4a,b. Morphology of as-spun BCZT-PVP green nanofibers are appeared as smooth, continuous and having diameter in the range of 250-400 nm. After sintering at 700 °C for 3 h, diameter of these nanofibers reduced to 80-250 nm due to the removal of organic materials.


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Surface of the sintered nanofibers are not quite smooth due to grain growth at high temperature as shown in the inset of Figure 4b. Also, nano size grains are densely stacked together in sintered fibers. Transmission electron microscope images (Figure 4c) of sintered BCZT nanofibers supported the crystalline nature of fibres with compact and continuous structure. High resolution TEM showed (Figure 4d) inter planer spacing 0.415 nm (inset shows surface profile plot) due to (101) plane. Furthermore, elemental analysis was carried out to calculate elemental composition and their distribution throughout the fibers. Elemental mapping is carried out in sintered BCZT nanofibers (Figure 5) and observed that all elements are homogenously distributed throughout BCZT nanofibers sheet. Elemental composition (barium, calcium, zirconium, titanium and oxygen) was measured and indicated in Table 2. Molecular formula is proposed as Ba0.85Ca0.15Zr0.1Ti0.9O3 from estimated atomic percentages, which is consistent to XRD results. 3.3. Dielectric study. Figure 6a shows the typical frequency dependent dielectric behaviour of sintered BCZT fibers. The lower value of permittivity (εr = 142) was observed due to porous structure of nanofibers mat. The dielectric constant of sintered nanofibers mat decreased with increase in frequency due to reduce polarization time at higher frequencies. Also, dielectric properties with respect to temperature were carried out for understanding the phase transition behaviour of nanofibers. The variation of dielectric constant as a function of temperature at frequency 1 kHz (Figure 6b) showed increase in dielectric constant with increase in temperature from 0-108 °C due to decrease of dipoles relaxation time. After that, dielectric constant decreased due to phase transformation from ferroelectric to nonferroelectric cubic phase. The Curie temperature (Tc) of BCZT nanofibers is found to be 108.8 °C, which is higher than bulk ceramic powder (80-85 °C).35-36 The electro-spun fibers have diameters in the range of 80-250 nm with much smaller grain size (10-20 nm). The reduced grain size of nanofibers causes large grain boundary density, which relieves internal



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stress in materials due to sliding of grain boundary. As a result, fine grain size decreases free energy of the ferroelectric phase, and thereby increases the Curie temperature of nanofibers.36 The frequency dependent imaginary part of electric modulus of sintered nanofibers at various temperatures (25-150 oC) is sown in Figure 7a. The imaginary part of modulus showed relaxation peak at room temperature due to induced relaxation. Relaxation process was examined through electric modulus formula: 37-38

∗ = + = ԑ∗ (1) Where and are real and imaginary part of the modulus, and ԑ∗ is the complex permittivity. Relaxation peak is observed at lower temperature in sintered nanofibers, which is shifted further towards higher frequency side with increase in temperature. The shifting of the relaxation peak is attributed to the characteristic of Maxwell–Wagner–Sillars (MWS) polarization.39 Induced relaxation is observed due to thermal fluctuations of lattices and interaction between ions, which is dissimilar in nature. Thereafter, the relaxation process is analysed further by plotting a graph between frequency maxima against reciprocal of temperature for finding the activation energy of developed nanofibers (Figure 7b). Nanofibers exhibited Arrhenius type behaviour and the activation energy was determined by using Arrhenius equation:40-41

= −

(2)

Where f and T are the frequency maximum and temperature in the electric modulus, Ea is the activation energy (determined from the slope) and k is the Boltzmann constant. Activation energy of sintered nanofibers was calculated and found to be 68.6 kJ/mole. Activation energy describes the minimum energy required for the mobile charge carrier to accumulate at interfacial regions under applied field and temperature.


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3.4. Demonstration of BCZT nanofibers based nanogenerator. Laterally aligned BCZT nanofibers based nanogenerator was fabricated using a simple and cost effective technique. Sintered BCZT nanofibers mat having thickness 6-10 µm was adhered on pre-cured RTV silicone elastomer, and packed between silicone layers. This flexible nanogenerator is demonstrated as vibration sensor and energy harvester by using tapping and vibration modes respectively (Figure 8a,b). The power generation mechanism and dipole alignment in nanogenerator are shown schematically in Figure 1. Whenever the nanogenerator undergoes alternating mechanical pressure on top of surface or in the longitudinal direction, it generates charge due to the creation of tensile and bending stress through polymer matrix and in-turn transfer to piezo-ceramic nanofibers. Generated potential is given by the following equation:42

∆V = g33 σ (l) dl

(3)

∆V is the voltage generated between the electrodes, g33 is the piezoelectric voltage constant, σ(l) is the stress function along the axial direction and l is the length of nanofiber across the adjacent electrodes in IDE pattern.41-42 Also, stress in the longitudinal direction σ(l) can be defined as !""

!##

!&&

( ) = − . % − . %

(4)

Where Ep is the modulus of BCZT fibers, E11 is the modulus of the composite, σxx, σyy, and σzz are stresses along the X, Y, Z directions respectively, and σ is the Poison ratio of the matrix. Hence, voltage generated by the nanogenerator for a given applied load can be written as

!""

!##

!&&

∆V = g33 − . % − . % dl


(5)


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Output voltage generated from the BCZT nanofibers based nanogenerator, when periodic dynamic load applied with finger on top of the nanogenerator. Positive and negative voltage were observed during tapping and shown in Figure 8a,b. Generated positive voltage appeared due to transient flow of electrons under the external load and negative voltage arisen in absence of external load due to the reverse flow of carriers, and resulted piezo-potential become non-existent. Under mechanical tapping on nanogenerator, it generated voltage repeatedly ranging from 3.5-17.4 V in an open circuit. Also, it generated voltage ranging from 0.7-1.3 V in bending mode. The open circuit maximum peak voltage generated ~17.4 V with corresponding current ~17.4 µA, which was recorded at high applied stress levels on the stack. In addition, few small peaks are observed in the voltage response due to the vibration of the stack and damping effect. Figure 9 shows the output current generated by nanogenerator when tapping on stack across the load resistance 1 MΏ. The peak voltage and power output are measured ~2.68 V and ~2.95 µW respectively during tapping under variable load resistance. The volume of BCZT nanofibers sheet is 1.5 x 10-3 cm3 (L- 20 mm, W- 15 mm and T-0.05 mm). Total power density is calculated around 491 µWcm-3, which is 45% higher than BCT-BZT nanowires based nanogenerator.12 Output voltage and current density (2.9 µA/cm2) are higher than earlier reported lead free piezo-ceramic based nanogenerator. The maximum output voltage (17.4 V) is five times more than BaTiO3 and BCT-BZT nanowire based nanogenerator.12,43 Also, current density (2.9 µA/cm2) of our developed nanogenerator is 26% more than NaNbO3 nanowire based nanogenerator.44-46 Output voltage generated by nanogenerator is two times more with 33% less current density than PMT-PT nanowire based nanogenerator.45 Enhanced piezoelectric effect of nanofibers mat might be observed due to the polarisation reorientation, which induced intermediate ferroelectric phase in the nanostructure.8,47


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Excellent flexibility, robustness and high Curie temperature (Tc) will make these nanogenerator as building block for power source. 4. CONCLUSIONS Lead free BCZT nanofibers mat was fabricated successfully by using electro-spinning technique. Ceramic-polymer precursor gel composition and sintering temperature are standardized before and after electro-spinning. Developed nanofibers mat was used further to fabricate a nanogenerator and characterized using analytical techniques. Embedding BCZT nanofibers in the soft matrix imparted requisite toughness and flexibility to nanogenerator structure, and protected from mechanical damage. Demonstration of BCZT nanofiber based nanogenerator was conducted by measuring output voltage in different modes. The maximum peak voltage and output current are achieved ~2.68 V and ~1.1 µA respectively. The output power obtained ~2.95 µW in developed nanogenerator, which might have potential application in the important technological areas. ACKNOWLEDGEMENT The authors thank the Director and all members of Ceramic Division, NMRL, DRDO for their support during technical work. REFERENCES (1) Pignolet, A.; Wang, L.; Proctor, M.; Levy, F.; Schmid, P.E. Raman Scattering Study of Lead Zirconate Titanate Thin Films Prepared on Silicon Substrates by Radio Frequency Magnetron Sputtering. J. Appl. Phys.1993, 74, 6625-6631. (2) Shaw, T.M.; Trolier-McKinstry, S.; McIntryre, P.C. The Properties of Ferroelectric Films at Small Dimensions. Annual Rev. Mater. Sci. 2000, 30, 263-298. (3) Chen, X.; Li, J. W.; Zhang, G. T.; Shi, Y. PZT Nanoactive Fiber Composites for Acoustic Emission Detection. Adv. Mater. 2011, 23, 3965-3969.



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Properties

of

Ba(Zr0.2Ti0.8)O3-(Ba0.7Ca0.3)TiO3

Piezoelectric Coefficients. Curr. App. Phys. 2011, 11, S120.


Ceramics

with

Huge


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

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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


Table Caption(s):

Table 1. Lattice parameters of sintered BCZT nanofibers

a (Å)

c (Å)

c/a

12.7

3.970

3.987

1.004

11.5

3.951

3.967

1.004

Temp.

Crystallite

(°C)

Size D (nm)

700 600

Table 2. Elemental analysis results of BCZT nanofibers

weight (%)

weight (%)

Theoretical Measured atomic (%) atomic (%)

Ba

52.4

52.8

17.00

17.59±0.4

Ca

2.7

2.5

2. 99

2.85±0.14

Ti

21.5

20.4

18.00

19.49±0.5

Zr

4.1

4.0

2.00

2.01±0.01

O

19.3

20.3

60.01

58.06±2.0

Element(s)

Theoretical Measured



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 Caption(s)

Figure 1. Schematic representation of BCZT-based nanogenerator.


Page 20 of 29

(0 2 2)

(1 1 2)

(0 1 2)

(0 0 2)

Intensity (a.u)

(1 1 1)

(1 1 0)

(a)

700°C

600°C

500°C 400°C 300°C

20

30

40

50

60

70

738

524

A1(LO3)/E(LO3)

A1(TO3)

E(TO2)

(b)

307

205

A1(TO2)

2θ ( degree)

Intesity (a.u.)

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


(1 0 0)

Page 21 of 29

200

400

600

800

1000

Raman Shift (cm-1) Figure 2. (a) XRD patterns of nanofibers mat at different sintering temperature (b) Raman spectra of sintered BCZT nanofibers.



Weight loss (%)

100

(a)

Sintered nanofibers

80 60 40

Green fibers

20 200

400

600

800

Temperature (oC)

(b) 3452 3450

1631

1442

600°C 500°C

3440

1610 1478

1388

1076

625

877

3446

1602 1463

400°C 300°C

3431

Green 3431

2919 2845

1667 1562 1432

1285

652

1034 935

1590

1392 1302

871

650

1082

1380

865

634

1056

Transmitance (%)

700°C

1631

1442

876

618

400

877

588

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 22 of 29

800 1200 1600 2000 2400 2800 3200 3600

Wave number (cm-1) Figure 3. (a) TGA curves of green and sintered nanofibers (b) FTIR spectra of green and sintered nanofibers at different temperatures.


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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 4. (a) SEM images of green BCZT nanofibers mat and (b) sintered BCZT nanofibers mat, (c) TEM image of sintered BCZT nanofibers (inset showing (101) plane) and (d) high resolution TEM image of BCZT nanofibers.



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 5. Elemental mapping of sintered BCZT nanofibers.


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Page 25 of 29

160 (a)

Dielectric constant

140 120 100 80 60 40 20 -1

0

10

10

1

10

2

3

10

10

4

10

5

10

6

10

Frequency (Hz) 210

TC- 108.8 °C

(b)

Dielctric constant

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


180 150 120 90 60 30 0

50

100

150

200

Temperature (°C) Figure 6. Dielectric behaviour of sintered BCZT nanofibers (a) frequency dependent and (b) temperature dependent.



0.40 25 oC 65 oC

(a)

0.35

Modulus''

45 oC 85 oC

105 oC 145 oC

0.30 0.25

125 oC 150 oC

0.20 0.15 0.10 0.05 0.00 0

1

10

10

2

10

10

3

10

4

5

10

6

10

7

10

Frequency (Hz) 14

(b)

Sintered Fibers

12

ln(Fmax)

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 26 of 29

10

8

6

Ea= 68.64 kJ/mole

4 0.0022 0.0024 0.0026 0.0028 0.0030 0.0032 0.0034

1/T

Figure 7. (a) Frequency dependent electric modulus behaviour of sintered BCZT nanofibers, and (b) corresponding Arrhenius plot.


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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 8. (a) Photograph of nanofibers mat during tapping, (b) Photograph of nanofibers mat during bending, (c) Measured output voltage during tapping and (d) Measured output voltage during bending.



20

Load-1 Mohm 15

Current (µΑ)

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

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10 5 0 -5 -10 0.0

0.5

1.0

1.5

2.0

2.5

Time (S) Figure 9. Output current with load resistant of 1 MΏ of nanogenerator under finger taping.


Table of Content

20 Voltage output Taping mode

Output voltage (V)

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


15 10 5 0 -5 -10

0

1

2

3

4

Time (S)

BCZT nanogenerator

Output voltage (V)

Page 29 of 29

1.5

Voltage output Bending mode

1.0 0.5 0.0 -0.5 -1.0

0

1

2 Time (S)


3

4

Fabrication of Large Aspect Ratio Ba0.85Ca0.15Zr0.1Ti0.9O3

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