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KxNa0.5-xBi4.46Ce0·04Ti4O15+y (x = 0, 0.04, 0.08, 0.12, 0.16, 0.20) ceramics were synthesized by solid state reaction. The microstructure and electrical properties of the solid solutions were characterized. It is found that the doping of appropriate amount of K improved the degree of lattice distortion of the material, and the characteristic parameter b/a of lattice distortion obtained the maximum value through structural refinement at x = 0.12. A defect dipole pair ( K B i ″ − V o • • ) is formed by adjusting the defects of the material. The polarizability of defects is 4.88 × 10-37F·m2. The formation of defect dipole pairs that deflect towards the direction of spontaneous polarization reduces the difficulty of polarization and improves the piezoelectric properties. Finally, the optimal piezoelectric coefficient (d33) of NBCT-xK ceramics is 23 pC/N, and the residual polarizability (2Pr) is 4.14 μC/cm2. The values of residual polarization rate (2Pr), piezoelectric coefficient (d33) and b/a show the same trend, which will gradually decrease when their value increases to a certain extent. The dielectric loss of all samples below 200 °C are lower than 0.01, and the dielectric constant is relatively flat below 400 °C. Moreover, the Curie temperature (Tc) of KxNa0.5-xBi4.46Ce0·04Ti4O15+ybased ceramics is increased to 686.0 °C, which will enable the ceramics to be used in oilfield logging, aerospace and military fields in high temperature environment.

Apart from discharge energy density (Wr) and discharging time (t0.9), thermal stability and anti-fatigue for charge-discharge performance are also the important performance indexes for dielectric pulsed capacitor. Na0.5Bi0.5TiO3 based ceramics are usually accompanied by huge electric field-induced strain when appling electric field, resulting in the fatigue phenomenon and thermal accumulation effect in the cycling process. In this work, Na0.5Bi0.5TiO3-xNaNbO3 (NBT-xNN) ferroelectric relaxor ceramic has been prepared by the solid state reaction process. The effect of NaNbO3 content on microstructures, impedance spectroscopy, electric-field-induced strain and charge-discharge performance of NBT-xNN ceramics have been investigated systematically. Results indicate the proper percent of NaNbO3 could favor the formation of polar nanoregions (PNRs), which leads to the diffusion of phase transition and the diminution of electromechanical strain. Therefore, the high thermal stability and anti-fatigue for charge-discharge property has been achieved in NBT-xNN ceramics. An enhanced discharging energy density of 2.44 J cm−3 along with discharge time of 0.31 μs could be obtained in the NBT-xNN with x = 0.3, and a very stable discharge energy density of 2.06 J cm−3 concomitantly with discharge time less than 0.37 μs could be gained in a wide temperature range of 20–150 °C with a fluctuation of ±4% after 104 charge/discharge cycles. This work would contribute to the development of charge-discharge system, especially dielectric capacitor, for green pulsed power devices.