High-Entropy La-(Bi_0.2Na_0.2Ba_0.2Sr_0.2Ca0.2)TiO₃ Ceramic with Ultrastable Dielectric Performance within 327-689 K and up to 7 GPa

To meet the needs of energy storage under high temperature and high pressure, a high-entropy relaxor ferroelectric ceramic, La-modified (Bi0.2Na0.2Ba0.2Sr0.2Ca0.2)TiO3 is prepared, which has excellent thermal and mechanical stability. At the wide temperature range of 327-689 K (tan delta < 0.01) and below approximate to 7 GPa, the material shows extraordinary functional performance. Comprehensive study indicates that the ceramic possesses a single-phase cubic perovskite structure, and as the pressure increases, the material undergoes a transition at approximate to 8 GPa, in which enormous large grains crack into smaller grains, but the space group Pm<(3)over bar>m does not change. In addition, with further compression, the grains begin to rotate and re-orientate at approximate to 9 GPa. Based on the investigations, it is considered that the suitable doping of multiple cations can effectively improve the stability of ceramics, and it also paves the experimental way to further study thermally and mechanically stable high-entropy ceramics.