Effect of Ta ⁵⁺ doping on the thermal physical properties of defective fluorite Y ₃ NbO ₇ ceramics

The effects of substituting the B cation in A 3 BO 7 ceramics on their thermal physical properties were investigated by applying a large mass difference. Y 3 (Nb 1‐x Ta x )O 7 (x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5) ceramics were synthesized, and their structural characteristics were determined. All the fabricated Y 3 (Nb 1‐x Ta x )O 7 ceramics showed defective fluorite structures and glass‐like low thermal conductivity (1.18−2.04 W/m∙K at 25°C) because of the highly distorted crystal structure and significant mass difference. Substitution with Ta 5+ enhanced the sintering resistance, leading to superior thermal‐insulating performance via grain boundary scattering. Furthermore, the ceramics exhibited excellent coefficients of thermal expansion, implying the promising applicability of Y 3 (Nb 1‐x Ta x )O 7 as new thermal barrier materials. The effect of mass difference on the thermomechanical properties of the ceramics was examined, suggesting a simple strategy for engineering the chemical composition of new thermal barrier materials.