First-principles investigation of cubic XGeO3 (X=Cu, In, Tl) germanates: Implications for thermal barrier and advanced engineering applications

High-temperature protective materials with combined thermal insulation, mechanical durability, and functional versatility are critical for next-generation turbine, aerospace, and energy systems. In this work, cubic XGeO 3 (X = Cu, In, Tl) germanate perovskites are systematically investigated using first-principles calculations to evaluate their potential as advanced thermal barrier coating (TBC) materials. Structural optimization and combined energetic ( E 0 , Δ E f ) and geometric (t, μ, τ) stability metrics confirm robust phase stability. Elastic constants satisfy the Born mechanical stability criteria, while positive Cauchy pressure and G/B ratios (< 0.571) indicate ductile behavior favorable for thermal shock resistance under cyclic service conditions. The calculated minimum thermal conductivity values of 1.059, 1.084, and 0.776 W/mK for CuGeO 3 , InGeO 3 , and TlGeO 3 , respectively, together with G/B ratios below the 0.571 threshold, meet key TBC performance criteria. TlGeO 3 exhibits the strongest intrinsic thermal insulation capability, highlighting its suitability for gas turbine hot-section components and thermally stressed structural coatings. Electronic structure analysis reveals magnetic semiconducting behavior in CuGeO 3 , whereas InGeO 3 and TlGeO 3 behave as non-magnetic metals, enabling tunable multifunctionality within the same materials platform. Optical calculations show strong visible–UV absorption and stable dielectric response, supporting potential integration into high-temperature optoelectronic and protective coating systems. These results identify XGeO 3 perovskites as emerging candidates for multifunctional thermal protection technologies, bridging thermal management, mechanical resilience, and functional electronic performance for advanced industrial applications. • Cubic XGeO 3 (X = Cu, In, Tl) perovskites are mechanically and thermodynamically stable with ductile elastic behavior. • Low minimum thermal conductivity (0.776–1.084 W/mK) and G/B < 0.571 satisfy key TBC criteria. • TlGeO 3 shows the strongest intrinsic thermal insulation for high-temperature coating applications. • CuGeO 3 exhibits ferromagnetic semiconducting behavior, enabling multifunctional thermal protection materials.