固相反应合成La_(1-x)Sr_xCr_(1-y)Mn_yO_(3-δ)过程热力学分析

Thermodynamic Analysis on Synthesis Process of La_(1-x)Sr_xCr_(1-y)Mn_yO_(3-δ) by Solid Reaction Method

把合成La1-xSrxCr1-yMnyO3-δ(LSCM)的物料进行混合、研磨和烧结。对合成过程中的各种物料行为进行分析,根据热力学数据ΔG和ΔH的计算结果,对物料之间可能发生的反应及产物分析预测,并根据吉布斯自由能最小原理,绘出不同温度下反应体系中组分的种类及含量图,确定合成LSCM的热力学条件。从热力学角度来看,钙钛矿在低温下就可生成,但是在低温下固相反应的动力学条件不足。用XRD,TG-DTA等检测手段对热力学分析结果进行了验证。实验结果显示,1000℃下烧结后,有较多钙钛矿生成,1250℃下烧结15 h后得到了单一钙钛矿型材料。

The raw material for synthesizing La1-xSrxCr1-yMnyO3-δ （ LSCM ） was mixed, ground and sintered. The performance of every raw material in the synthesis process was studied. According to the thermodynamic data ΔG and ΔH counted by HSC Chemistry 5 software, one can make a predictions on the possible reactions and products by the Gibbs energy minimization technique were made. The results show that the formation of perovskite phase is thermodynamically possible but the reaction is hampered by the kinetic conditions at low temperature. XRD and TG-DTA techniques were adopted to certify the analysis results. The experimental results show that much perovskite crystallines begin appear at 1000 ℃ and pure perovskite phase is observed after the raw material was sintered at 1250 ℃ for 15 h in the solid state reaction process.