Microstructure and dielectric behavior of Bi₂O₃-doped KSr₂Nb₅O₁₅ ceramics

Bi₂O₃-doped KSr₂Nb₅O ₁₅(KSNB) ceramics with relative density higher than 96% were successfully prepared by sintering at 1300°C. The addition of Bi ₂O₃ will decrease the tetragonal degree of the materials, improve the densification, and promote the grain growth of KSNB ceramics. Relaxation behavior can be observed in KSNB ceramics, which is attributed to the complex response of the polar nanoregions and matrices resulting from substitution of Bi³⁺ for Sr²⁺ and K⁺. Bi ₂O₃-doped KSr₂Nb₅O₁₅ ceramics show good temperature-dependence performance and high dielectric tunability. KSNB ceramics with 4.0 wt% added Bi₂O₃ show the maximum tunability, and capacitance changes with temperature meet the requirement of the X7R standard, which makes these ceramics promising candidate materials for multilayer capacitors and tunable phase shifters.