Homogenizing energy landscapes and microstructure enabling a linear and stable thermal sensing response in high-entropy niobates

Advanced temperature-sensitive materials play an increasingly important role in modern hypersonic propulsion technology. For such applications, ensuring long-term high-temperature (above 1000 °C) stability is key to enabling integrated structural and functional capabilities. Herein, we develop a Mo-regulated high-entropy ferroelastic niobate strategy for ultrawide-temperature negative-temperature-coefficient thermosensitive ceramics. Density functional theory (DFT) calculations show that the A-site high-entropy facilitates Mo doping in (Ca_0.2La_0.2Ce_0.2Eu_0.2Gd_0.2)NbO₄. Consequently, Mo doping broadens the distribution of local atomic configurations, modulates ferroelastic domain structures, and increases atomic-scale displacement disorder. These structural changes redistribute Hall transport contributions and reduce the mismatch between grain and grain-boundary transport barriers. As a result, the developed ceramics exhibit highly linear Arrhenius behavior (R² = 0.99907) over an ultrawide temperature range from −50 to 1250 °C, accompanied by a low B-value fluctuation of only 4.44%. High-temperature impedance analysis further confirms closely matched grain and grain-boundary activation energies, with a minimum activation-energy mismatch ( $\mathrm{\Delta }{E}_{\text{a}}$) of only 0.009 eV. During aging at 1250 °C, the ceramics exhibit aging-induced postdensification accompanied by an increase in relative density and strain redistribution, resulting in excellent long-term stability with a stabilized-stage resistance drift as low as 1.09% after 1000 h. These findings demonstrate that manipulating entropy-stabilized defects provides a robust pathway to decouple sensitivity from degradation in functional ceramics under thermal stress.