Preparation And Properties Study Of Bi_0.5Na_0.5TiO₃-BaTiO₃-KNbO₃Based Energy Storage Dielectric Ceramics

High energy density dielectrics are crucial in miniaturization of power pulsesystem. Antiferroelectric materials have excellent storage performance. But with thelead-free requirements for environment protection, it is imperative to find lead-freematerials whose energy storage properties are comparable to that of lead-basedmaterial. Recently, Bi0.5Na0.5TiO3(BNT) based ceramics have been widely studiedfor energy storage. It has high Curie temperature (TC=320℃) and displaysantiferroelectric features between Tdand Tm(200-320℃). Transition betweenantiferroelectric and ferroelectric under an application electric field lead totremendous storage and release energy, which makes BNT-based materials tobecome an phase transition energy storage materials with high temperature stabilityand high density. However, it is hard but important to slim the hysteresis loop underthe premise of keeping the large polarization intensity through modification on BNTbased cermaics. By this method, higher energy density and energy storage efficiencywill be obtained. In this paper, we modified0.93Bi0.5Na0.5TiO3-0.07BaTiO3usingKNbO3solution method, in order to fabricate lead-free antiferroelectric ceramicswith high energy storage performance.[0.93Bi0.5Na0.5TiO3-0.07BaTiO3]-xKNbO3((1-x)BNTBT-xKN) ceramics arefabricated by traditional solid state method. XRD analysis suggests formation ofsingle perovskite structure, and with increasing of KN, the coexistence ofrhombohedral phase and tetragonal phase transit to the tetragonal phase. Electricproperties analysis shows that, with increasing of KN content, the phase transitiontemperature reduced. At room temperature, hysteresis loops shows pinched and slimP-E loops which is related to relaxor antiferroelectric features. With the addition ofKN, ceramics show excellent storage properties, under the10Hz,6kV/mm, forcomposition of9KN, the energy storage density reached to0.51J/cm3, storageefficiency reached to78%, which is comparable to the lead-based antiferroelectricceramics. The temperature stability of energy density is good. 0.93Bi0.5Na0.5TiO3-0.07BaTiO3(BNTBT) and KNbO3(KN) powders with anaverage particle size of~50nm and~200nm were synthesized respectively by sol-gelmethod and hydrothermal method. The two kinds of powders were then ball-milledand BNTBT-xKN ceramics were obtained. The dielectric and energy-storageproperties were investigated. All the ceramic samples are in single perovskitestructure, indicating that KN can solute into BNTBT totally within the studiedcomposition range. In addition, ceramics are sintered densely with homogeneousgrain size. Dielectric and ferroelectric measurement reveals that hysteresis loops atroom temperature become slimmer due to the reduced depolarization temperaturewith the increasing of KN content, which largely improved energy-storage densityand efficiency. Compared to conventional solid state method, the ceramics fabricatedby wet-chemical method possess higher breakdown strength and larger energystorage density. At room temperature, for13KN, energy storage density reached1.41J/cm3under12.5kV/mm. For5KN, there was excellent high-temperature energystorage performance, which energy density at125℃reached0.64J/cm3(6kV/mm),energy storage efficiency reached85%. These suggest5KN may be a promisingenergy storage materials which will applicate in high temperature.