Effect of Y2O3 doping on thermophysical properties and grain growth rate of lanthanum zirconate

Abstract

Notwithstanding the impressive phase stability and low thermal conductivity exhibited by lanthanum zirconate (LZ), its low coefficient of thermal expansion is deemed a paramount limitation. In the present study, (La1-xYx)2Zr2O7 with x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, as new TBCs, were synthesized by reverse co-precipitation and calcination method. The XRD and Raman analyses elucidated that the substitution of Y3+ ions occurred exclusively at the La3+ positions. In addition, in accordance with FESEM and DTA findings, the incorporation of Y2O3 has induced a reduction in particle size and an enhancement in crystallization resistance. The evaluation of the coefficient of thermal expansion (CTE) demonstrated a notable improvement following the introduction of Y2O3. Specifically, the CTE of LZ increased from 9.34 × 10−6 °C-1 to 10.5 × 10−6 °C-1 in the case of (La0.5Y0.5)2Zr2O7 at 1100oC. Investigations of phase stability following a 50 h heat treatment at 1300oC indicated that Y2O3 had no impact on phase stability. All compounds, similar to LZ, exhibited excellent phase stability. Furthermore, the addition of Y2O3 significantly amplified the grain boundary diffusion mechanism during heat treatment, leading to an accelerated grain growth rate. The grain growth rate increased from 1.7 nm/h at LZ to 2.2 nm/h in the case of (La0.6Y0.4)2Zr2O7.