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利用XRD和DTA/TG系统地研究了石榴石结构的Li_7La_3Zr_2O_(12)(LLZO)的形成机制,所用原料为LiOH·H_2O。研究发现,LLZO是通过以下化学反应形成的:7Li_2O+3La_2O_3+4ZrO_2=2Li_7La_3Zr_2O_(12)。XRD结果表明,LLZO大约在680℃开始生成,这与DTA/TG曲线上的放热峰比较吻合,这个放热峰是由LLZO相生成引起的。LLZO相在比较宽的温度范围内(720~1000℃)能稳定存在。然而,当温度高于1000℃,由于锂元素的严重挥发缺失,LLZO是不稳定的,会分解为焦绿石相的La_2Zr_2O_7。随着煅烧温度的升高,分解产物的量越来越多,LLZO逐渐减少。当反应混合物在较低的煅烧温度时,所生成的物质经鉴定是镧的化合物,这是因为La_2O_3非常容易吸收水汽和CO_2,LLZO粉末在800℃利用固相反应法合成。经研究发现,LLZO晶体属于四方晶系。由扫描电镜观测显示,所制备的LLZO粉末是纳米尺度的。
The formation mechanism of Li_7La_3Zr_2O_ (12) (LLZO) with garnet structure was systematically investigated by XRD and DTA / TG. The raw materials used were LiOH · H_2O. The study found that LLZO is formed by the following chemical reaction: 7Li_2O + 3La_2O_3 + 4ZrO_2 = 2Li_7La_3Zr_2O_ (12). XRD results showed that LLZO started to form at about 680 ℃, which was in agreement with the exothermic peak on the DTA / TG curve. This exothermic peak was caused by the LLZO phase. LLZO phase in a relatively wide temperature range (720 ~ 1000 ℃) can exist stably. However, when the temperature is higher than 1000 ℃, LLZO is unstable and decomposes into La_2Zr_2O_7 in the pyrochlore phase due to the absence of severe volatilization of lithium. With the calcination temperature increases, the amount of decomposition products is more and more, LLZO gradually decreased. The resulting material was identified as a lanthanum compound when the reaction mixture was at a lower calcination temperature because La 2 O 3 absorbed water vapor and CO 2 very easily and the LLZO powder was synthesized by solid phase reaction at 800 ° C. The study found that, LLZO crystal belongs to the tetragonal system. Scanning electron microscopy showed that the prepared LLZO powder was nanoscale.