Effects of dielectric thickness on energy storage properties of 0.87BaTiO3-0.13Bi(Zn2/3(Nb0.85Ta0.15)1/3)O3 multilayer ceramic capacitors

Abstract

Multilayer Ceramic Capacitors (MLCCs) for energy storage applications require a large discharge energy density and high discharge/charge efficiency. Here, 0.87BaTiO3-0.13Bi(Zn2/3(Nb0.85Ta0.15)1/3)O3 (BTBZNT) powders were synthesized via solid-state reactions, and MLCCs with sub-micron grains were fabricated using a two-step sintering method. The BTBZNT MLCCs, which are well-defined relaxor ferroelectrics, possessed relatively high permittivity, dielectric sublinearity, and negligible hysteresis. An AC breakdown strength (BDS) enhancement from 511 to 1047 kV/cm was obtained as the dielectric thickness (D) decreased from 26 to 5 μm. The strong correlation between BDS and D, described asBDS∝D−0.368, agreed well with the general macroscopic theory of thermal breakdown in insulators. The enhanced BDS afforded the BTBZNT MLCCs (D∼9 μm) with excellent energy storage properties with a maximum discharge energy density of 10.5 J/cm3 and discharge/charge efficiency of 93.7% under a maximum electric field of 1000 kV/cm. The MLCCs also exhibited excellent thermal stability with discharge energy density variation <±5% over a wide temperature range of −50 to 175 °C under an electric field of 400 kV/cm. These remarkable performances make BTBZNT MLCCs promising for energy storage applications.