Phase stability and grain growth in (La_0.25Gd_0.25Yb_0.25Y_0.25)₂Zr₂O₇ high entropy rare earth zirconate

The current study aims to synthesize, characterize, and investigate the sintering and phase stability behavior of a multi-cation rare-earth zirconate LaGdYbYZO: (La_0.25Gd_0.25Yb_0.25Y_0.25)₂Zr₂O₇. The synthesis of the LaGdYbYZO powder was carried out using a co-precipitation method. The successful synthesis of this powder with a single phase fluorite structure and an average crystallite size of 230 Å at 1100 °C for 10 h has been demonstrated by the results of phase and micro structural investigations. The synthesized powder was evaluated for sintering resistance and phase stability at 1100, 1200, and 1300 °C for 50 h. The distribution of lanthanum(III), gadolinium(III), ytterbium(III), yttrium(III) ions in the “A” sites and zirconium(IV) ions in the “B” sites of the A₂B₂O₇ structure was examined aSt 1100, 1200, and 1300 °C. The results showed a growing trend in the phase transformation tendency from defect fluorite to pyrochlore structure during the heat treatment process. The slight growth rate of particle sizes in the LaGdYbYZO powder was measured at rates of 1.32 nm.h⁻¹, 1.16 nm.h⁻¹, and 1.11 nm.h⁻¹ at 1100, 1200, and 1300 °C, respectively.