Ultrahigh energy density with excellent thermal stability in lead-free multilayer ceramic capacitors via composite strategy design

Abstract

Dielectric capacitors have received growing interest for application in advanced electrical and electronic systems. However, the low energy density and poor thermal stability at high temperature severely hinder their practical applications. Herein, novel relaxor ferroelectric 0.4((Bi_0.5Na_0.5)TiO₃)-0.6(0.87BaTiO₃-0.13Bi(Zn_2/3(Nb_0.85Ta_0.15)_1/3)O₃) (0.4BNT-0.6BTBZNT) multilayer ceramic capacitors (MLCCs) with low-cost 70 Ag/30 Pd inner electrodes were prepared via composite strategy design. The 0.4BNT-0.6BTBZNT dielectric materials combine the complementary advantages of both BNT and BTBZNT and enable a great improvement of the maximum dielectric constant and stable temperature range of the dielectric constant, leading to higher energy density and better thermal stability. Therefore, an ultrahigh discharge energy density (U_d) of 14.49 J cm⁻³ and an energy efficiency (η) of 84.9% have been obtained. Moreover, the MLCCs possess a good thermal stability with U_d variations of <±7% and η > 85% from 25 to 170 °C, and an excellent cycling stability with minimal U_d variations <±3.3% (5.49 ± 0.18 J cm⁻³) after 100k charge–discharge cycles. Overall, the 0.4BNT-0.6BTBZNT MLCCs are highly promising and significant for practical commercial high energy storage applications, and the composite strategy design can play an effective role in designing high energy storage performance and high thermal stability dielectric capacitors for power electronic and pulse power applications.