Phase Structure Evolution, Dielectric Thermal Stability, and Energy Storage Performance of Sr2+ Modified La3+ and Nb5+ Co-Doped Na0.5bi0.5tio3 Based Lead-Free Ceramics Via Viscous Polymer Process

Abstract

Due to the recent trend towards to miniaturization and the severe requirements in electronic components as well as the integrated microelectronic devices, there is an urgent necessity to develop stable and high-performance dielectric ceramics for energy storage. Within the current investigation, La3+ and Nb5+ were initially co-doped into Na0.5Bi0.5TiO3 ceramics to improve the shape of electric hysteresis loop and form half a dielectric platform. Subsequently, Sr2+ was further introduced into Na0.5Bi0.46La0.04Ti0.96Nb0.04O3.02 synchronously with a preparation optimization via viscous polymer process in order to furtherly enhance the energy storage performance (ESP) and optimize the stability of dielectric constant with temperature. The phase structure evolution, microstructure, and dielectric and ferroelectric properties as well as the simulation calculation have been deeply studied. With an increase in Sr2+ doping, ceramics transform from tripartite and tetragonal phases to orthorhombic phase, and finally stabilize in the state of pseudo-cubic phase. The emergence of a dielectric platform widens the applicability of ceramics. The finite element simulation has indicated that a smaller grain size possesses a positive effect on the critical breakdown electric field, and relaxation transformation benefits the reduction of Pr. The resulting Na0.35Bi0.31Sr0.3La0.04Ti0.96Nb0.04O3.02 ceramics achieved 6.69 J/cm3 of Wrec and 89.48% of η under a 400 kV/cm electric field, with a release time (t0.9) of 0.168 μs for 90% of the energy under a 280 kV/cm electric field, and a Pd of 148 MW/cm3. This study demonstrates multiple steps to modify the dielectric and ferroelectric properties of Na0.5Bi0.5TiO3 based ceramics, and provides an effective way to expand working temperature ranges as well as improving energy storage performance.

Keywords: Ceramics, Phase evolution, Dielectric platform, Energy storage performance.