Defect Engineering and High‐Entropy Strategies for Enhanced Energy Storage and Thermal Response in Ferroelectric Ceramics

Abstract Stable and efficient thermal runaway pulse alarm systems are critical for safeguarding personnel in high‐risk operations. High‐entropy ceramic capacitors (HECCs) exhibit exceptional discharge power and thermal stability, making them promising candidates for such applications. However, the inevitable increase in polarization hysteresis caused by defect dipoles, which originates from increased entropy and structural disorder that deteriorates the ferroelectricity of the system, has posed significant limitations on the development of HECCs. Here, BaTiO 3 ‐based high‐entropy systems coexisting with polymorphic relaxor phases and octahedral tilts are designed based on an electrical neutral strategy and first‐principles calculations. The optimized high‐entropy ceramics are fabricated via a sequential process involving tape‐casting, isostatic pressing, and oxygen annealing. This approach effectively eliminates internal defects while achieving a high recyclable energy storage density of 10.63 J cm −3 and an energy storage efficiency of 90.11% at 770 kV cm −1 . Additionally, the anomalous fluorescence thermal enhancement effect of the ceramics is explored for its potential in real‐time temperature sensing. By highlighting the application of the HECCs in uncontrolled temperature pulse alarms within high‐risk environments, the limitations of conventional ceramics (e.g., inadequate energy supply and susceptibility to thermal runaway) will be addressed, thereby offering an effective strategy for high‐performance energy storage ferroelectrics.