Effect of Raw Material Particle Size on the Synthesis of La2Zr2O7 by the Molten Salt Method.

Abstract

In this study, a process based on the molten salt method was proposed to prepare La2Zr2O7 for improving the kinetic conditions of synthesis. Considering that the particle size of raw materials is an important factor that may have an effect on the kinetic process of synthesis, ZrO2 and La2O3 with different particle sizes are used as raw materials, and the synthesis experiment is carried out at 900-1300 °C through the combination of raw materials with different particle sizes. The results show that the particle size of ZrO2 plays an important role in the synthesis of La2Zr2O7. The "dissolution precipitation" mechanism of the synthesis process in the NaCl-KCl molten salt was confirmed by SEM image observation. Furthermore, the influence of the dissolution rate of each raw material on the synthesis reaction was studied by introducing the Noyes-Whitney equation and testing the specific surface area and solubility of each raw material, and it was confirmed that the particle size of ZrO2 was the limiting condition of the synthesis reaction, and use of ZrO2(Z50) with a nominal particle size of 50 nm could significantly improve the kinetic condition of the reaction, thus reducing the synthesis temperature, which can help realize the energy-saving and -efficient synthesis of pyrochlore La2Zr2O7.