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.

With the rapid development of communication technology, multifunctional ceramics that integrate microwave dielectric and negative temperature coefficient (NTC) thermistor properties have met the evolving needs of electronic components. Although conventional spinel oxides excel in single functionalities, they struggle to simultaneously achieve linear NTC behavior and stable microwave dielectric performance over a wide temperature range. To address this, the role of Sc³⁺ substitution in modifying Mg_0.8Mn_0.2Al_1.6Fe_0.4O₄ ceramics was systematically investigated. The results demonstrate that Sc³⁺ substitution effectively inhibits oxygen vacancy formation and achieves the ratio regulation of the Mn²⁺/Mn³⁺ and Fe³⁺/Fe²⁺ bimetallic redox pairs, which significantly improves the material constant B (B_200/1000°C = 8367–9758 K) and enables linear resistance–temperature curves (lnρ–1000/T) within a broad temperature range (200–1000 °C). Additionally, the ceramics exhibit optimal microwave dielectric properties: low dielectric constants (ε_r = 8.86–10.55), ultrahigh quality factors (Q∙f = 96,000–149,000 GHz), and near-zero temperature coefficients of resonant frequency (τ_f = −33.2×10⁻⁶ to −10.2×10⁻⁶ °C⁻¹), resulting from Sc³⁺-induced lattice stabilization and octahedral bond-valence strengthening effects. A cylindrical dielectric resonator antenna (CDRA) fabricated from Mg_0.8Mn_0.2Al_1.3Sc_0.3Fe_0.4O₄ achieves 92% radiation efficiency and 6.28 dBi gain at 12 GHz, validating its potential for Ku-band satellite communication. This work reveals that Sc³⁺ substitution synergistically enhances both the microwave dielectric and thermosensitive functionalities of Mg–Al–Mn–Fe–O spinel ceramics, offering a breakthrough in material design for next-generation multifunctional communication devices.