Investigations of atomic disorder and grain growth kinetics in polycrystalline La2Zr2O7

Abstract

In the present study, we investigated the impact of annealing temperature and time on grain growth and atomic order/disorder in La2Zr2O7 pyrochlore. Experimental results showed that the sample remains in the pyrochlore phase at higher annealing temperature (1500\xa0°C) for a longer time (96\xa0h). The influence of grain growth and atomic order/disorder on the structural properties could be effective in designing and tailoring the pyrochlore materials for energy applications. La2Zr2O7 with different degrees of atomic order was prepared by isothermal annealing at different temperatures (1200\xa0°C, 1300\xa0°C and 1500\xa0°C) for various annealing time (24, 48, and 96\xa0h). Structural and microstructural properties of La2Zr2O7 were investigated using the X-ray diffraction, and Raman spectroscopy techniques. The degree of cation–anion order increases with increasing annealing temperature and time. The curvature-driven grain coarsening of the small grains favored the formation of larger grains. The grain-growth kinetics is studied using the Arrhenius equation $$G_{t}^{n} - G_{0}^{n} = k_{0} \\exp \\left( { - \\frac{{E_{\\text{a}} }}{RT}} \\right)t^{q}$$Gtn-G0n=k0exp-EaRTtq and activation energy for grain growth is found to be 590\u2009±\u200921\xa0kJ/mol. A quantitative analysis has been presented to investigate the cation/anion order and microstructural evolution in pure phase polycrystalline La2Zr2O7.