Dual Real‐Time Response to Lattice Distortion and Temperature Fields in Energy‐Storage Ceramics

Simultaneously achieving sensitive lattice-distortion detection and high capacitive energy storage in dielectric ceramics is critically demanded yet challenging for fail-safe aerospace systems. Herein, a novel high-low valence co-substitution strategy is designed for a NaNbO₃-based relaxor ferroelectric with the composition (1-x)[0.85(Na0.94Yb0.01Tm0.01)NbO₃-0.15(Bi0.5Na0.5)TiO₃]-x(Ba0.5Sr0.5)(Sn0.5Hf0.5)O₃. The severe valence imbalance triggers a spontaneous Bi3+/5+ self-compensation mechanism, driving Bi migration from A- to B-site. This unique configuration induces intense lattice distortion, which substantially lowers the energy barrier for splitting Tm³⁺ 4f orbitals and activates a new electronic state (³F'2|3). Consequently, a direct correlation between lattice distortion and rare-earth luminescence is established, enabling real-time assessment via photoluminescence peak splitting. Concurrently, Yb³⁺/Tm³⁺ co-doping bestows anomalous thermally enhanced fluorescence for temperature sensing. Furthermore, the dual-site Bi substitution facilitates a local coexistence of polymorphic relaxor phases (rhombohedral-orthorhobic-tetragonal-cubic), yielding a high breakdown strength of 785 kV cm⁻¹ and an outstanding recoverable energy density of 13.73 J cm⁻³ with 94.24% of efficiency. This work provides a paradigm for developing multifunctional materials capable of atomic-resolution operando monitoring and superior energy storage in extreme environments.