Optimization Of Energy Storage Performance Of Strontium Barium-Based Tungsten-Based Bronze Ferroelectric Ceramics With Niobate

Dielectric ceramic capacitors have been widely developed and applied in recent years due to the advantages of high withstand voltage,good temperature stability and low raw material cost.However,most of the research on dielectric capacitor energy storage only revolves around perovskite structural ceramics,and the research results are relatively lopsided,which cannot meet the growing demand for energy storage.In order to further improve the energy storage performance of dielectric ceramic capacitors,it is urgent to develop new potential energy storage materials.Tungsten bronze materials with excellent dielectric and ferroelectric properties and flexible adjustment are attracting more and more attention in the field of dielectric ceramic capacitor development.Among them,as a typical unfilled tungsten bronze structural ceramic,Sr_xBa_1-xNb₂O₆（SBN,0.25≤x≤0.75）is a typical unfilled tungsten bronze（TB）structural ceramic.It has a high dielectric constant and flexible structure,which is conducive to the design of more potential energy storage materials.However,pure SBN has problems such as difficult preparation and weak relaxation,which limits its energy storage application.In view of the characteristics of SBN ceramics,three innovatively design schemes are proposed in this study,which are as follows:（1）The breakdown strength of SBN ceramic is improved by sintering method to improve the energy storage performance.By adjusting the Sr/Ba ratio to adjust the relaxation of SBN ceramic,when Sr:Ba=7:3,the SBN ceramic obtained an effective energy storage density of 1.87 J/cm³ and an efficiency of about 90%.Furthermore,the abnormal growth of grain size of SBN ceramic at higher temperatures was suppressed by a two-step sintering process（the first step was to raise the temperature to 1450℃at10℃/min without heat preservation,the second step was to rapidly reduce the temperature to 1325℃at 10℃/min for 12 h）,Improve the breakdown strength of ceramics.（2）The ferroelectric behavior and storage properties of Sr_0.6Ba_0.4Nb₂O₆（SBN60）ceramic are regulated based on A-site ion substitution.(Sr_0.6Ba_0.4)_1-x(Bi_0.5K_0.5)_xNb₂O₆and(Sr_0.6Ba_0.4)_1-x(Bi_0.5Na_0.5)_xNb₂O₆ ceramics system were constructed by doping Bi,K and Bi,Na in the same proportion at A-site,respectively.The results show that the introduction of Bi,K and Bi,Na not only reduces the residual polarization and enhances the relaxation of ceramics,but also reduces the grain size of the SBN60 ceramic and improves the breakdown strength.（3）The ferroelectric behavior and energy storage properties of SBN60 ceramic are regulated based on the substitution of B-site ions.Sr_0.6Ba_0.4Nb_1-xTa_xO₆and Sr_0.6Ba_0.4Nb_1-xSb_xO₆ ceramics system were constructed by doping Ta and Sb via B site,respectively.The results show that the introduction of Ta and Sb not only effectively enhances the relaxation of ceramics,but also reduces the grain size and increases the breakdown strength of SBN60 ceramic.