Homogenizing energy landscapes and microstructure enabling a linear and stable thermal sensing response in high-entropy niobates
Advanced temperature-sensitive materials are critical for hypersonic propulsion and next-generation energy systems, yet long-term stability above 1000 °C remains a formidable barrier. Conventional transition-metal spinel oxides (e.g., Ni–Mn–Co–O) suffer phase decomposition and cation migration above 300 °C, causing exponential resistance drift. This work develops a Mo-regulated high-entropy ferroelastic niobate strategy for ultrawide-temperature negative-temperature-coefficient (NTC) thermosensitive ceramics. Density functional theory calculations reveal that A-site high-entropy facilitates Mo doping in (Ca0.2La0.2Ce0.2Eu0.2Gd0.2)NbO4. Mo doping broadens local atomic configurations, modulates ferroelastic domain structures, and increases atomic-scale displacement disorder, redistributing Hall transport contributions and reducing grain/grain-boundary transport barrier mismatch. The optimized HEN-0.2Mo ceramic exhibits highly linear Arrhenius behavior (R² = 0.99907) from −50 to 1250 °C with a B-value fluctuation of only 4.44%. High-temperature impedance analysis confirms closely matched grain and grain-boundary activation energies (Eg = 1.209 eV, Egb = 1.218 eV; ΔEa ≈ 0.009 eV). During 1250 °C aging, postdensification and strain redistribution yield a stabilized-stage resistance drift of only 1.09% after 1000 h. These findings demonstrate that entropy-stabilized defect engineering decouples sensitivity from degradation in functional ceramics under thermal stress.