Improved thermal barrier properties of InFeZnO₄ ceramics by Gd/Yb doping

As one of new candidate ceramic materials for thermal barrier coatings (TBCs), In_1-xYb(Gd)_xFeZnO₄ (x = 0, 0.1, 0.2) ceramics were synthesized by solid-state reaction at 1400°C for 24 h. The phase stability and thermophysical properties of In_{1- x}Yb(Gd)_xFeZnO₄ compounds were investigated. XRD results indicated that single phase In_1-xYb(Gd) _xFeZnO₄ were successfully synthesized and no phase transformation occurred during heating to 1400°C. Yb/Gd doped InFeZnO ₄ ceramics revealed relatively lower thermal conductivities than the undoped ceramics. The thermal conductivity of In_0.8Gd _0.2FeZnO₄ was 1.2 W m^-1 K^-1, about 14% lower than that of InFeZnO₄. The thermal expansion coefficients of In_1-xYb(Gd)_xFeZnO₄ (x = 0.1, 0.2) ceramics were in a range of 12.3 × 10^-6 K^-1 - 12.6 × 10^-6 K^-1 at 1000°C, which are similar to that of InFeZnO₄ ceramics.