Unique growth manner of Li5La3Ta2O12 crystals from lithium hydroxide flux at low temperature
Unique growth manner of Li5La3Ta2O12 crystals from lithium hydroxide flux at low temperature
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氢氧化锂熔剂低温下Li5La3Ta2O12晶体的独特生长方式
DOI：
10.1021/acs.cgd.5b00672
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发表时间：
2015
影响因子：
3.8
通讯作者：
Katsuya Teshima
中科院分区：
文献类型：
--
作者：
Xiong Xiao;Hajime Wagata;Fumitaka Hayashi;Hitoshi Onodera;Kunio Yubuta;Nobuyuki Zettsu;Shuji Oishi;Katsuya Teshima
石榴石型Li 5 + xLn 3 MIV 2-yMVyO 12 +z（x，y= 0-2，z= 0-1; Ln = La，Pr，Nd; M = Ta，Zr，Nb）化合物是一种很有前途的锂离子导电固体电解质，但其生长方式尚不清楚。在此，自形Li 5La 3 Ta 2 O 12单晶的低温生长作为保温温度和时间，冷却速率，熔剂类型和溶质浓度的函数的分析揭示了一个独特的生长方式。Li 5La 3 Ta 2 O 12晶体在500 °C下由LiOH助熔剂生长，并在700 °C下转化为Li 7 La 3 Ta 2 O 13。在500 °C保温过程中形成的准钙钛矿型LiLa 2 TaO 6相，随着保温时间的延长，有效地转变为Li 5La 3 Ta 2 O 12相。Li 5La 3 Ta 2 O 12单晶的生长与冷却速率无关，但受助熔剂种类和溶质浓度的影响。较低的溶质浓度（1或5摩尔%）是获得良好分散和自形单晶的关键。最佳生长条件为：保温温度500 °C，溶质浓度1或5mol%，保温时间10 h。这些结果表明，Li 5La 3 Ta 2 O 12单晶的形成和生长不仅受助熔剂生长过程的控制，而且还涉及溶质与LiOH助熔剂之间的化学反应。最后，高分辨率透射电子显微镜图像和选定区域的衍射图案突出显示具有高结晶度和发育良好的{110}和{211}面的产品。
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 manner is still unclear. Herein, the analysis of the low-temperature growth of idiomorphic Li5La3Ta2O12single crystals as a function of holding temperature and time, cooling rate, flux type, and solute concentration revealed a unique growth manner. Li5La3Ta2O12crystals were grown at 500 °C from LiOH flux and transformed into Li7La3Ta2O13at 700 °C. The pseudo-perovskite-type LiLa2TaO6phase, initially formed during the holding at 500 °C, was efficiently transformed into the Li5La3Ta2O12phase with increasing holding time. The growth of Li5La3Ta2O12single crystals was independent of the cooling rate but was affected by the 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 Li5La3Ta2O12single crystals are not only controlled by a general flux growth process but also involve chemical reactions between solutes and LiOH flux. Finally, high-resolution transmission electron microscopy image and selected area diffraction pattern highlighted products with high crystallinity and well-developed {110} and {211} facets.