Unique Growth Manner of Li5La3Ta2O12 Crystals from Lithium

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Unique Growth Mode of Li5La3Ta2O12 Crystals from Lithium Hydroxide Flux at Low Temperature Xiong Xiao, Hajime Wagata, Fumitaka Hayashi, Hitoshi Onodera, Kunio Yubuta, Nobuyuki Zettsu, Shuji Oishi, and Katsuya Teshima Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.5b00672 • Publication Date (Web): 06 Aug 2015 Downloaded from http://pubs.acs.org on August 13, 2015

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Crystal Growth & Design

Cover page Unique Growth Mode of Li5La3Ta2O12 Crystals from Lithium Hydroxide Flux at Low Temperature Xiong Xiao,† Hajime Wagata,‡ Fumitaka Hayashi,‡Hitoshi Onodera,‡ Kunio Yubuta,¶ Nobuyuki Zettsu, ‡,ǁ Shuji Oishi,§ Katsuya Teshima*‡,ǁ † Department of Materials Science and Engineering, Interdisciplinary Graduate School of Science and Technology, Shinshu University, Wakasato, Nagano 380-8553, Japan ‡ Department of Environmental Science and Technology, Faculty of Engineering, Shinshu University, Wakasato, Nagano 380-8553, Japan ¶ institute for Materials Research, Tohoku University, Sendai 980-8577, Japan ǁ Center for Energy and Environmental Science, Shinshu University, Wakasato, Nagano 380-8553, Japan § Shinshu University, Asahi, Matsumoto, 390-8621, Japan ABSTRACT

Garnet-type Li5+xLn3MIV2-yMVyO12+z (x, y = 0–2, z = 0–1; Ln = La, Pr, Nd; M = Ta, Zr, Nb) compounds are promising Li-ion conducting solid electrolytes, but their growth mode is still unclear. Herein, the analysis of the low-temperature growth of idiomorphic Li5La3Ta2O12 single crystals as a function of holding temperature and time, cooling rate, flux type, and solute concentration revealed a unique growth mode. Li5La3Ta2O12 crystals were grown at 500 °C from LiOH flux, and transformed into Li7La3Ta2O13 at 700 °C. Pseudo-perovskite-type LiLa2TaO6 phase, initially formed during the holding at 500 °C, was efficiently transformed into Li5La3Ta2O12 phase with increasing holding time. The growth of Li5La3Ta2O12 single crystals was independent of the cooling rate, but was affected by flux type and solute concentration. A low solute concentration (1 or 5 mol%) was the key to obtain well-dispersed and idiomorphic single crystals. The optimum growth conditions involved a holding temperature of 500 °C, a solute concentration of 1 or 5 mol%, and a holding time of 10 h. These findings indicate that formation and growth of Li5La3Ta2O12 single crystals are not only controlled by a general flux growth process, but also involve chemical reactions between solutes and LiOH flux. Finally, high-resolution TEM and selected area diffraction images highlighted products with high crystallinity and well-developed {110} and {211} facets.

* Corresponding author: Katsuya Teshima, Center for Energy and Environmental Science, Shinshu University, Wakasato, Nagano 380-8553, Japan. TEL: +81-26-269-5541; FAX: +81-26-269-5550; E-mail: [email protected]

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Unique Growth Mode of Li5La3Ta2O12 Crystals from Lithium Hydroxide Flux at Low Temperature Xiong Xiao,† Hajime Wagata,‡ Fumitaka Hayashi,‡Hitoshi Onodera,‡ Kunio Yubuta,¶ Nobuyuki Zettsu, ‡,ǁ Shuji Oishi,§ Katsuya Teshima*‡,ǁ †

Department of Materials Science and Engineering, Interdisciplinary Graduate School of Science and Technology, Shinshu University, Wakasato, Nagano 380-8553, Japan

‡

Department of Environmental Science and Technology, Faculty of Engineering, Shinshu University, Wakasato, Nagano 380-8553, Japan ¶

ǁ

institute for Materials Research, Tohoku University, Sendai 980-8577, Japan

Center for Energy and Environmental Science, Shinshu University, Wakasato, Nagano 3808553, Japan §

Shinshu University, Asahi, Matsumoto, 390-8621, Japan

* Corresponding author, E-mail: [email protected]


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ABSTRACT

Garnet-type Li5+xLn3MIV2-yMVyO12+z (x, y = 0–2, z = 0–1; Ln = La, Pr, Nd; M = Ta, Zr, Nb) compounds are promising Li-ion conducting solid electrolytes, but their growth mode is still unclear. Herein, the analysis of the low-temperature growth of idiomorphic Li5La3Ta2O12 single crystals as a function of holding temperature and time, cooling rate, flux type, and solute concentration revealed a unique growth mode. Li5La3Ta2O12 crystals were grown at 500 °C from LiOH flux, and transformed into Li7La3Ta2O13 at 700 °C. Pseudo-perovskite-type LiLa2TaO6 phase, initially formed during the holding at 500 °C, was efficiently transformed into Li5La3Ta2O12 phase with increasing holding time. The growth of Li5La3Ta2O12 single crystals was independent of the cooling rate, but was affected by kind of flux and solute concentration. A low solute concentration (1 or 5 mol%) was the key to obtain well-dispersed and idiomorphic single crystals. The optimum growth conditions involved a holding temperature of 500 °C, a solute concentration of 1 or 5 mol%, and a holding time of 10 h. These findings indicate that formation and growth of Li5La3Ta2O12 single crystals are not only controlled by a general flux growth process, but also involve chemical reactions between solutes and LiOH flux. Finally, high-resolution TEM and selected area diffraction images highlighted products with high crystallinity and well-developed {110} and {211} facets.


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INTRODUCTION Garnet-type Li5+xLn3MIV2-yMVyO12+z (x, y = 0–2, z = 0–1; Ln = La, Pr, Nd; M = Ta, Zr, Nb) compounds function as solid electrolytes in all-solid-state lithium-ion batteries (LIBs), because of their three-dimensional Li-ion pathway and high chemical stability.1–6 Among these garnets, Li6.75La3Zr1.75Nb0.25O12 shows the highest lithium ion conductivity, ~ 8 × 10−3 S·cm−1 at room temperature.7 Interestingly, a corresponding theoretical value of ~ 1 × 10−2 S·cm−1 was reported for Li6.75La3Zr1.75Ta0.25O12, although the reported experimental value is only 8.7 × 10−4 S·cm−1.8,9 This discrepancy could reflect the presence of particle boundary as well as the impurity phases of the Li6.75La3Zr1.75Ta0.25O12 sample.8 This highlights the need for the underlying method that efficiently grows the garnet-type crystals. Generally, garnet-type materials are prepared by solid-state reaction (SSR) methods above 800 °C.8,10 However, the high-temperature synthesis presents environmental and cost issues. Whereas tetragonal Li7La3Zr2O12 is commonly prepared by SSR method at 1250 °C, Il’ina and coworkers recently reported the successful synthesis of Li7La3Zr2O12 at lower (900 °C) temperature using the citrate-nitrate method, thanks to the intermediate compounds (Li2ZrO3, La2Zr2O7) formed during the synthesis.11 This result indicates that suitable intermediates can lower the formation temperature of the target products by altering the reaction path. The flux method, a liquid-phase single crystal growth technique used to prepare inorganic materials, is a promising approach for controlling the final shape of single crystals and to lower reaction temperatures.12,13 Awaka14 and Tietz15 et al. reported preparing Li7La3Zr2O12 single crystals at around 1000 °C in two steps using Li2CO3 flux. Kimijima et al.16 successfully grew Li7La3Zr2O12 single crystals at 700 °C using LiOH flux in one step. These results indicated that alkali metal hydroxide fluxes were effective for the crystal growth of mixed oxides at low temperatures, due to their low melting


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point and high solubility behavior.12,17 We have previously reported the growth of garnet-type Li5La3Nb2O12 single crystals at 500 °C by the LiOH flux method.18 Roof et al.6 also reported the synthesis of Li5La3Ta2O12 single crystals using the LiOH·H2O flux method at 600 °C in a closed silver tube. These results indicated that LiOH represent an effective flux to decrease the reaction temperature and form single crystals. Nevertheless, the growth mode of garnet single crystals under such conditions remains unknown. In this study, garnet-type Li5La3Ta2O12 was selected as a model material because of its promising properties as solid electrolyte. The crystal structure is shown in Figure 1. We explored different LiOH flux growth conditions (involving variable holding temperatures, solute concentrations, holding times, and cooling rates), and analyzed the corresponding formation behavior. The characterization of the species formed at the various stages of the synthesis allowed us to discuss the growth mode. To the best of our knowledge, this is the first work where the formation of idiomorphic Li5La3Ta2O12 single crystals is discussed.

EXPERIMENTAL SECTION Li5La3Ta2O12 crystals were prepared by the flux method. La2O3 (99.99%) and Ta2O5 (99.9%) powders were used as solutes, whereas LiOH·H2O (98%) was employed as flux as well as solute. The growth conditions are summarized in Table 1. The total mass of all reagents was fixed to approximately 10 g in each run. After mixing, each mixture was put into an alumina crucible with a volume of 30 cm3. The crucibles were loosely covered with an alumina lid and placed into a programmable furnace, followed by heating at 500 °C·h-1 and then holding for 10 h at the respective holding temperature. After heating, the crucibles were cooled to 100 ºC at a cooling rate of 10, 200, or > 9000 ºC·h-1 under air. A cooling rate > 9000 °C·h-1 indicates that the


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crucible was immediately removed from the furnace after heating. The products were separated from the remaining flux using hot water (~ 80 ºC). Scanning electron microscopy (SEM, JEOL, JCM-5700) images were acquired at an acceleration voltage of 15 kV. The average particle size was calculated over a sample of more than 300 crystals observed in the SEM images. Transmission electron microscopy (TEM, TOPCON, EM-002B) data were obtained at an acceleration voltage of 200 kV. X-ray diffraction (XRD) analyses were performed on a powder diffractometer (RIGAKU, MiniflexII) operating at 30 kV and 20 mA, using Cu Kα radiation (λ = 0.15408 nm). The XRD data for Rietveld refinement were collected in the 2θ range from 5 º to 120 º with a step of 0.012 º on a powder diffractometer (RIGAKU, SmartLab) operating at 40 kV and 40 mA, using Cu Kα radiation (λ = 0.1540593 nm). The whole pattern matching refinements of parameters of samples prepared at 500 ºC and 700 ºC (flux, LiOH; solute conc., 5 mol%; holding time, 10 h) were carried out using Rietveld analysis PDXL software (RIGAKU).

RESULTS AND DISCUSSION Effects of Holding Temperature and Time The effect of the holding temperature on crystal growth was first examined, keeping the solute concentration to 5 mol%. Figure 2 shows the XRD patterns of products flux-grown at various temperatures. At 400 ºC, no Li5La3Ta2O12 phase was obtained and all the diffraction peaks were attributed to La(OH)3 (Figure 2a), which is formed from the reaction of La2O3 with LiOH and the hydration of the remaining La2O3 during the washing process with hot water (see Figure S1). At 500 ºC, all diffraction peaks were attributed to Li5La3Ta2O12 without impurity phases (Figure 2b). Upon increasing the holding temperature to 700 ºC, the peaks were shifted to lower angles


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(Figure 2c and Figure S2), indicating the conversion of Li5La3Ta2O12 to Li7La3Ta2O13. Figure 2d, e shows observed, calculated, and difference patterns for Rietveld refinement of products prepared at 500 ºC (Run 2) and 700 ºC (Run 3). The details of the structure refinement are listed in Table S1. The lattice parameters of Li5La3Ta2O12 and Li7La3Ta2O13 were determined to be a = 1.280601(12) nm and 1.29071(12) nm, which values are in good agreement with the literature values, 1.2804 nm and 1.286 nm, respectively. 10, 19 Figure 3 shows the SEM images of the products grown at various holding temperatures. The morphology of flux-grown crystals was markedly dependent on the temperature. The growth at 400 ºC yielded particles with undefined shapes, but the increase in temperature to 500 ºC produced uniform, idiomorphic single crystals with average size of ~ 36.5 µm (Figure 3c, 3d). A further increase in temperature to 700 ºC led to a larger particle size and to significant porosity (Figure 3e, 3f). The pores formed in Li7La3Ta2O13 are clearly visible in Figure S3. These data are indicative of the reaction of Li5La3Ta2O12 with Li2O to form Li7La3Ta2O13. The holding time dependence at 700 ºC shown in Figure S4 further supports this finding. The effect of the holding time at 500 ºC was then investigated, in order to understand the formation pathways of Li5La3Ta2O12. The holding temperature and solute concentration were 500 ºC and 5 mol%, respectively, and the growth conditions are summarized in Table S2. Figure S5 and S6 show XRD patterns and SEM images of the crystals. Holding for 1 h resulted in coexisting Li5La3Ta2O12 and LiLa2TaO6 phases. Extending the holding time over 5 h provided a pure Li5La3Ta2O12 phase without byproducts, and the morphology of products changed from undefined particulate shapes to idiomorphic ones. Since the pseudo-perovskite-type LiLa2TaO6 was generated at an early stage of the reaction, this phase can be regarded as an intermediate for the Li5La3Ta2O12 formation. It is worth noting that the average crystal size increased gradually


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with time (37.2 µm for 5 h, 36.5 µm for 10 h, and 43.2 µm for 20 h), whereas the degree of flux evaporation was not affected and remained very low (< 5 wt.%), indicating that the evaporation of flux had no effect on crystal growth. Effect of Cooling Rate In general, the cooling rate can affect supersaturation and promote crystal growth. Figure S7 shows the XRD and SEM results of flux-grown Li5La3Ta2O12 crystals obtained with a cooling rate of 10 ºC·h-1 or by air-quenching (> 9000 ºC·h-1). The phase, size, and shape of the crystals were not affected. Based on the observed cooling rate as well as holding time dependence, it can be concluded that the Li5La3Ta2O12 crystal formation and growth are not only controlled by a dissolution and precipitation in which change the supersaturation caused by cooling, evaporation of flux and flow solute from a hotter to a cooler region are generally thought as driving force, but also by a chemical reaction between the solute components and the LiOH flux. Effect of Flux To determine the influence of LiOH flux, we compared the crystals discussed above with those grown from other fluxes with lower melting temperatures, such as NaOH, KOH, and LiNO3, whose melting point is 250 ºC, 320 ºC, and 404 ºC, respectively. Li5La3Ta2O12 crystals were also grown by the SSR method at 500 ºC for 10 h for comparison. The growth conditions are summarized in Table S3, and the XRD patterns of the products are shown in Figure S8. The observed diffraction peaks were assigned to La2O3, LiTaO3, and LiLa2TaO3 in each case, showing no formation of the Li5La3Ta2O12 phase. The considerable difference between the crystals grown with LiOH and with the other flux systems or without flux could be due to the different degree of dissolution of solutes (La2O3 and Ta2O5) and other kinds of alkaline


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components in the solvent. For instance, in general the solubility of oxides is lower in LiNO3 than in LiOH.17,21 Effect of Solute Concentration The effect of solute concentration on the crystal growth was then investigated, in order to understand the unique crystal shape of Li5La3Ta2O12. Figure 4 shows the XRD patterns of crystals grown at solute concentrations of 1, 5, 10, 20, and 30 mol% (runs 5, 2, 6, 7 and 8, in Table 1, respectively). A single Li5La3Ta2O12 phase was obtained in each run at 20 mol% or below. An increase in solute concentration to 30 mol% caused the occurrence of impurity La(OH)3 and LiLa2TaO6 phases, as a result of insufficient supply of Li source. The SEM images of Li5La3Ta2O12 crystals grown at various solute concentrations (Figure 5) highlight a change in particle morphology with increasing solute concentration. Relatively uniform particles of approximately the same size were obtained at 1 and 5 mol%. When the solute concentration reached 10 and 20 mol%, the crystals aggregated and their size became smaller (Figure 5f, 5h). Moreover, the crystal shape became undefined, a completely different behavior compared to crystals grown at low (1 and 5 mol%) solute concentrations. This reduction in crystal size was attributed to the generation of a greater number of nuclei for higher solute concentrations. Growth Mode Based on the above results, herein we discuss the possible formation manner of idiomorphic Li5La3Ta2O12 single crystals with uniform size and particle shape from LiOH at low solute concentration. The crystal formation is schematically illustrated in Figure 6. At the early stage of the SSR process, LiLa2TaO6 intermediates with pseudo-perovskite-type structure are formed around 500 ºC, as shown in Equation 1: 2 La2O3 + Ta2O5 + 2 LiOH → 2 LiLa2TaO6 + H2O

(1)


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During the holding at 500 ºC, Ta2O5 was gradually dissolved in LiOH flux, and the resultant TaOx species and LiOH reacted together with LiLa2TaO6 to form Li5La3Ta2O12, as illustrated in Equation 2: 6 LiLa2TaO6 + Ta2O5 + 14 LiOH → 4 Li5La3Ta2O12 + 7 H2O

(2)

No idiomorphic single crystals were formed in this step and the generated particles were markedly small (< 2 µm), as summarized in Figure S5a and S6a. The Li5La3Ta2O12 crystals were not completely dissolved in the LiOH flux during holding at 500 ºC, but part of the crystals, especially their surface, would dissolve and re-precipitate, leading to the formation of specific facets. Such repeated dissolution-precipitation processes combined with the chemical reactions of Equations 1 and 2 allow the formation of the idiomorphic Li5La3Ta2O12 crystals, which was highlighted in Figure S6c. Unfortunately, too long holding caused the rough surface of Li5La3Ta2O12 crystals (Figure S6d). On the other hand, at 700 ºC the LiOH flux gradually decomposed to Li2O and H2O, according to Equation 3: 2 LiOH → Li2O + H2O

(3)

The resultant Li2O then reacted with Li5La3Ta2O12 to form lithium-rich Li7La3Ta2O13 on the bases of XRD result in Figure 2c. The reaction is shown in Equation 4: Li5La3Ta2O12 + Li2O → Li7La3Ta2O13

(4)

The formation of pore in Li7La3Ta2O13 crystals (Figure 3f) could be due to the decomposition of Li5La3Ta2O12 and the addition reaction of Equation 4. Finally, we used TEM analysis to investigate the crystal structure of the idiomorphic Li5La3Ta2O12 single crystals obtained from run 2 in Table 1. Figure 7a shows the selected area electron diffraction (SAED) pattern of single crystals. Highly ordered SAED spots can be clearly


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observed, indicating high crystallinity. On the basis of the SAED pattern in Figure 7a, the d21-1 spacing was determined to be 0.524 nm, which is in excellent agreement with the theoretical value of 0.523 nm.20 Figure 7b shows a lattice image of the flux-grown Li5La3Ta2O12 single crystal, taken with the incident beam pointing along the [120] direction. The absence of any obvious defects in these images further confirms the high crystallinity of the obtained single crystals. The lattice parameter of the Li5La3Ta2O12 single crystals was determined to be a = 12.80601(12) Å from the XRD pattern in Figure 2b, which is consistent with the literature value of 12.804 Å.10 Figure S9 shows the XRD pattern of Li5La3Ta2O12 single crystals without previous grinding. The intensity ratio of {110} to {211} is 10.5, higher than that calculated from the corresponding International Center for Diffraction Data (ICDD) Powder Diffraction File (PDF) data (pattern #45-0110, Int. {110} / Int. {211} = 1.2). This finding indicates that {110} faces are predominant on Li5La3Ta2O12 crystals. Figure 7c shows a schematic illustration of a Li5La3Ta2O12 single crystal, mainly exposing {110} and {211} faces, drawn using crystallographic data from the literature.22 Notably, the illustration is in excellent agreement with the observed shape of the flux-grown Li5La3Ta2O12 single crystals (Figure 7d), leading us to conclude that Li5La3Ta2O12 single crystals are dominated by {110} and smaller-area {211} faces.

CONCLUSIONS We reported the low-temperature growth of idiomorphic Li5La3Ta2O12 single crystals from LiOH flux and investigated their growth mode under different crystal growth conditions. Li5La3Ta2O12 crystals were grown at 500 ºC, and transformed to Li7La3Ta2O13 at 700 ºC as a result of the reaction of Li5La3Ta2O12 with Li2O. The holding time dependence experiments indicated that the pseudo-perovskite-type LiLa2TaO6 is a key intermediate for the formation of


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Li5La3Ta2O12. On the other hand, the evaporation ratio and cooling rate did not affect the phase and morphology of crystals. Low solute concentrations (1 or 5 mol%) improved the shape and dispersity of the crystals. These results indicate that the idiomorphic Li5La3Ta2O12 crystals are formed from LiOH flux through the combination of the chemical reaction of Equation 2 with repeated dissolution-precipitation processes, as summarized in Figure 6. Because this represents a different crystal formation process compared to conventional flux growth, the present research has the potential to open a new avenue for the fabrication of other garnet-type materials.

ACKNOWLEDGMENT This work was supported by the Center of Innovation Program, “Global Aqua Innovation Center for Increasing Water-Sustainability and Improving Living Standards in the World” from Japan Science and Technology Agency, JST, and the Grant-in-Aid for Exploratory Research (Research No. 26630331). We gratefully acknowledge Mr. Tomohiko Yamagami at the Technical Division in Shinshu University for performing the cross-sectional SEM analysis.

Supporting Information Tables summarizing various growth conditions of Li5La3Ta2O12, along with XRD patterns and SEM images of products prepared under those conditions. This material is available free of charge via the Internet at http://pubs.acs.org.

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FIGURES

.

(a)

3

La(OH)3

Si (standard)

Intensity (10 counts)

Figure 1. Schematic representation of the crystal structure of garnet-type Li5La3Ta2O12.

Intensity (a.u.)

(b)

(d)

15 10 5 0 20

ICDD-PDF (39-0898) Li La Ta O 7 3 2 13 10

20

30

40

50

60

70

2 θ / degree

80

60 2θ / °

80

100

120

(e) 8

3

ICDD-PDF (45-0110) Li La Ta O 5 3 2 12

40

12

(c)

Intensity (10 counts)

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4 0 20

40

60

80

100

120

2θ / °

Figure 2. XRD patterns of samples prepared at (a) 400 ºC, (b) 500 ºC, (c) 700 ºC for 10 h using LiOH as flux; the observed (+), calculated (solid line), and their difference patterns (bottom) for the Rietveld refinement using XRD data of samples prepared at (d) 500 ºC, (e) 700 ºC. Solute conc., 5 mol%. The Powder Diffraction File (PDF) patterns of Li5La3Ta2O12 and Li7La3Ta2O13 extracted from the ICDD database are also shown.


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Page 16 of 21

Figure 3. SEM images of samples prepared with different holding temperatures: (a, b) 400 ºC, (c, d) 500 ºC, and (e, f) 700 ºC. Flux, LiOH; solute conc., 5 mol%; holding time, 10 h.


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La(OH)3

LiLa2TaO6 (a)

Intensity (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


(b) (c) (d) (e) ICDD-PDF (45-0110) Li5La3Ta2O12

10

20

30

40

50

60

70

80

2 θ / degree

Figure 4. XRD patterns of samples prepared from different solute concentrations: (a) 1 mol%, (b) 5 mol%, (c) 10 mol%, (d) 20 mol%, and (e) 30 mol%. Flux, LiOH; holding temp., 500 ºC; holding time, 10 h. The PDF pattern of Li5La3Ta2O12 extracted from the ICDD database is also shown.


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Figure 5. SEM images of samples prepared from different solute concentrations: (a, b) 1 mol%, (c, d) 5 mol%, (e, f) 10 mol%, (g, h) 20 mol%, and (i, j) 30 mol%. Flux, LiOH; holding temp., 500 ºC; holding time, 10 h.


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Figure 6. Schematic illustration of the proposed formation manner of idiomorphic Li5La3Ta2O12 single crystal from LiOH flux at 500 ºC. Solute conc., 5 mol%.

Figure 7. (a) SAED pattern, (b) lattice image, (c) schematic illustration, and (d) SEM image of Li5La3Ta2O12 crystals grown under optimum conditions. Flux, LiOH; holding temp., 500 ºC, solute conc., 5 mol%; holding time, 10 h.


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TABLES Table 1. Growth Conditions of Li5La3Ta2O12 Crystals from LiOH Flux.

Holding temp.

Holding Solute time LiOHa La2O3

Flux Ta2O5

(ºC)

(h)

(g)

(g)

1

400

10

1.083

2

500

10

3

700

4

LiOH

Solute conc.

Cooling rate

(g)

(g)

(mol%)

(ºC·h-1)

2.522

2.281

4.115

5

200

1.083

2.522

2.281

4.115

5

200

10

1.083

2.522

2.281

4.115

5

200

900

10

1.083

2.522

2.281

4.115

5

200

5

500

10

0.396

0.923

0.834

7.841

1

200

6

500

10

1.382

3.219

2.911

2.488

10

200

7

500

10

1.604

3.736

3.378

1.283

20

200

8

500

10

1.694

3.947

3.568

0.791

30

200

Run

a

a

LiOH·H2O


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For Table of Contents Use Only

Unique Growth Mode of Li5La3Ta2O12 Crystals from Lithium Hydroxide Flux at Low Temperature Xiong Xiao,† Hajime Wagata,‡ Fumitaka Hayashi,‡Hitoshi Onodera,‡ Kunio Yubuta,¶ Nobuyuki Zettsu, ‡,ǁ Shuji Oishi,§ Katsuya Teshima*‡,ǁ

Low-temperature growth of Li5La3Ta2O12 single crystals from LiOH was achieved. During the flux growth, pseudo-perovskite-type LiLa2TaO6 was efficiently transformed to Li5La3Ta2O12. A low solute concentration was turned out to be a key factor for the formation of well-dispersed crystals with idiomorphic shapes.


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Unique Growth Manner of Li5La3Ta2O12 Crystals from Lithium

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