Preparation of ultra-fine La₃NbO₇ powder by solid state reaction

As a new candidate material for the ceramic layer in thermal barrier coatings (TBCs) system, La₃NbO₇ was synthesized with La₂O₃ powder and Nb₂O₅ powder by solid state reaction. The starting powders with a mole ratio of La to Nb of 3:1 were mixed and then the mixture was calcined under the different temperatures (800°C, 1000°C, 1200°C) and dwell times (2h, 6h, 10h). The phase structure of the powder was observed by X-ray diffraction (XRD), and the microstructure of the sample was observed by scanning electron microscope (SEM). The effect of calcination temperature and dwell time on the phase formation were examined. The results indicate that the La₃NbO₇ powder with single phase can be synthesized successfully at 1200°C for 10h in air, and the La₃NbO₇ powders synthesized have an ultra-fine particle size of 0.5∼1μm with a granular particle shape. With the temperature increasing, LaNbO₄ was synthesized firstly and then La₃NbO₇ was synthesized with a mole ratio of La ₂O₃ to LaNbO₄ of 1:1.