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

ABSTRACT 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 NaNbO 3 ‐based relaxor ferroelectric with the composition (1‐ x )[0.85(Na 0.94 Yb 0.01 Tm 0.01 )NbO 3 ‐0.15(Bi 0.5 Na 0.5 )TiO 3 ]‐ x (Ba 0.5 Sr 0.5 )(Sn 0.5 Hf 0.5 )O 3 . The severe valence imbalance triggers a spontaneous Bi 3+/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 Tm 3+ 4 f orbitals and activates a new electronic state ( 3 F′ 2|3 ). Consequently, a direct correlation between lattice distortion and rare‐earth luminescence is established, enabling real‐time assessment via photoluminescence peak splitting. Concurrently, Yb 3+ /Tm 3+ 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.