自蔓延高温合成La1-xSrxMnO3过程中杂质产生原因的热力学分析

Thermodynamic Study of Impurity Forming in Preparing La1-xSrxMnO3 by Self-Propagating High-Temperature Synthesis Method

摘要:

热力学计算和实验分析相结合，分析了自蔓延高温合成La1-xSrxMnO3过程中杂质产生的原因并给出了消除杂质的方法。结果表明：当采用Mn02稀释剂时，由于生成La2SrO4的吉布斯自由能与生成SrMnO3的自由能相当，自蔓延高温合成产物中容易生成La2SrO4杂质相，采用La1-xSrxMnO3作稀释剂，可以避免La2SrO4的产生；当稀释剂较多时，合成产物中容易产生Mn3O4杂质相，消除的方法是控制稀释剂添加量，控制自蔓延反应速度和体系温度。

Abstract:

Through thermodynamic calculation and experiment analysis, the cause of impurity forming in preparing La1-xSrxMnO3 by self-propagating high-temperature synthesis (SHS) was studied and the suggestion was given in this paper to avoid or diminish it. The results show that La2SrO4 impurity was produced inevitably in the products synthesized by SHS because the Gibbs free energy of La2SrO4 forming reaction is equivalent to that of SrMnO3 forming reaction when MnO2 was adopted as dilution. When La1-xSrxMnO3 was used as dilution, La2SrO4 forming could be avoided. The over-dilution of La1-xSrxMnO3 resulted in Mn3O4 impurity forming, which could be avoided by adjusting the proportion of dilution and controlling the reaction speed and system temperature of SHS process.