A New Family of High Temperature Stability And Ultra-Fast Charge-Discharge Knn-Based Lead-Free Ceramics

Abstract

Dielectric ceramic capacitors have been widely used in pulse-power technology because of their good performance of high power density and fast discharge speed. A series of lead-free relaxor ceramics (1-x)K_0.5Na_0.5NbO₃-xLa(Mn_0.5Ni_0.5)O₃(abbreviated as (1-x)KNN-xLMN) featuring with considerable charge-discharge behavior and energy storage properties were designed and prepared in this work. La(Mn_0.5Ni_0.5)O₃ incorporation can not only inhibit the growth of grain but also induce the dielectric relaxation behavior. After doping, the grain size of ceramics decreases to 180±20 nm, and the diffusion factor is >1.6, both of which are beneficial to obtain slender P-E loops and improve the energy storage performance of the ceramics. Consequently, an acceptable dielectric properties (dielectric permittivity maximum ε_r  of 1693, Δε/ε_{100 ℃} ≤15% from 33℃ to 309℃ dielectric loss minimum tan δ of 0.028, 50 kHz) and a high recoverable energy storage density (W_rec ~ 1.65 J/cm³) accompany with high energy storage efficiency (η~ 76%) is attained simultaneously in 0.97KNN-0.03LMN ceramics. Meanwhile, this optimal composition also exhibits satisfactory charge-discharge performance (P_D ~ 155 MW/cm³, t_0.9 ~ 55 ns) and temperature stability (30 ~ 110℃ ). All these merits indicate that 0.97KNN-0.03LMN ceramics have potential application value in future
advanced pulsed power capacitors.

Keywords: Lead-Free Ceramics, Relaxor Ferroelectric, Ultra-Fast Charge-Discharge, High Energy Storage Density