Study On Cold Sintering Process And Energy Storage Properties Of Sr_0.7Bi_0.2TiO₃ Dielectric Ceramics

Energy storage components have a wide range of applications,such as hybrid vehicles,integrated circuits,solar photovoltaic,and so on.Compared with fuel cells,batteries and supercapacitors,dielectric capacitors have attracted much attention because of their ultra-high power density.Their charge and discharge time only in the order of nanoseconds to microseconds,so they are widely used in pulse circuits and have irreplaceable roles in various fields.However,the energy density of dielectric capacitor limits its further application.In addition,dielectric ceramics are currently commonly prepared by traditional solid-state sintering methods,and due to the need for long-term high-temperature treatment,grain coarsening can easily lead to poor breakdown strength and energy storage density.In order to reduce the grain size of ceramics.Based on the typical Sr_0.7Bi_0.2TiO₃（SBT）relaxor ferroelectric ceramics,this work studied the effect of cold sintering process（CSP）on the dielectric energy storage of ceramics.Firstly,the influence of different sintering aids on the CSP of SBT ceramics was studied.With Sr（OH）₂·8H₂O,Suspension of C₄H₆O₄Srand C₁₆H₃₆O₄Tiand CH₃COOH,Suspension of SrCl₂and nano TiO₂,When Sr（OH）₂·8H₂O is uesd for sintering aids,the relative density of SBT ceramics is the highest,reaching 83.48%.But it can not meet the density requirements of energy storage ceramics.This may be due to Sr（OH）₂·8H₂O is used as a sintering aid to form amorphous grain boundaries,resulting in large flaky grains.The mechanical properties of SBT ceramics prepared with suspension of C₁₆H₃₆O₄Tiand CH₃COOH as sintering aids are poor,and complete ceramics cannot be obtained.This may be because CSP of SBT ceramics is not suitable for acidic environments.When SBT ceramics are prepared in a suspension of SrCl₂and nano TiO₂,single step CSP cannot form a dense filling at the pores of the ceramic particles.Secondly,the suspension of SrCl₂and nano TiO₂was mixed with SBT powder,the grain size was controlled by CSP,and high-temperature treated ceramics.Ceramic heat treated at 1170℃achieving the balance between grain size（0.5μm）and relative density（98.47%）.The ceramic has a high recoverable energy storage density of 3.32 J/cm³,a high efficiency of 92.84%,a fast discharge rate of 61.7 ns,and a high hardness of～8.73 GPa.These excellent properties show that CSP has great potential in the preparation of dielectric energy storage ceramics.Finally,the application of CSP in the preparation of SBT ceramics by SPS is explored.Ceramic has small grain size of 0.184μm,high relative density of 97.21%,and small dielectric constant of about 1100.The experimental results show that the CSP/SPS hybrid preparation technology can produce dielectric ceramics in a short time while inhibiting the growth of ceramic grains.But there are many variable factors in the preparation of ceramics by SPS,its mechanism needs to be further studied.