Study On The Preparation Technology And Energy Storage Performance Of BNT-BT Ceramics

Dielectric energy storage ceramic material is considered as an excellent candidate material for pulse power energy storage capacitors because of its high energy density and fast charge and discharge rate.At present,most energy storage materials contain lead,which hinders their practical application.Therefore,the development of lead-free dielectric energy storage ceramic materials with high energy storage density has become a current research hotspot.The high saturation polarization strength（P_S～40μC/cm²）and high dielectric constant（～800）of BNT based ceramics are favorable for energy storage.In order to improve the energy storage density of ceramics,it is urgent to reduce the residual polarization intensity and increase the voltage withstand value（E_b）.In this paper,the solid-phase sintering method was used to prepare BNT based ceramics.The effects of the proportion of Bi and Na ions at A position and the solution of the third group Ag NbO₃ and Sr TiO₃ on the phase structure,grain size,dielectric,ferroelectric,compressive strength and energy storage properties of Bnt based ceramics were studied.Pure perovskite 0.94(Bi_0.5+xNa_0.5-x)TiO₃-0.06Ba TiO₃（BNT-BT）lead-free ceramics were prepared by solid phase sintering.With the increase of x value,the temperature Ts corresponding to the dielectric anomaly peak gradually drops from 180℃to near room temperature,and the temperature stability of the dielectric constant increases.The P-E curve test shows that the saturation polarization strength of the ceramics first increases and then decreases,and the residual polarization strength of the ceramics decreases nonlinearly.The ceramics exhibit a double hysteresis loop similar to antiferroelectric,which effectively improves the energy storage performance.With the increase of x value,the grain size of the ceramics decreases gradually from 1.09μm to 0.78μm,and the compressive strength E_b of the ceramics increases significantly.Dielectric spectrum shows:As x increases from 0 to 0.035,the dielectric constant of ceramics increases from 655 to 1880,suggesting an improvement in energy storage density performance,which is consistent with the calculation of energy storage density.When x=0.035,the effective energy storage density of BNT-BT ceramics sintered at1130℃～2 h reaches the maximum(W_rec=1.137 J/cm³),and the corresponding energy storage efficiencyηis 60.7%.（1-x）[0.94(Bi_0.535Na_0.465)TiO₃-0.06Ba TiO₃]-x Ag NbO₃（BNT-BT-AN）lead-free ceramics were prepared by solid phase sintering.SEM test shows that with the introduction of the third group of Ag NbO₃,the grain size decreases first and then increases.Compared with pure BNT-BT,the introduction of Ag NbO₃ significantly increases the dielectric constant of ceramics at room temperature fromε_r=1000 toε_r=2000.The compressive strength of the ceramics increased from 10 k V/mm to 14 k V/mm,and the saturation polarization strength of the ceramics remained high at 47μC/cm²,which effectively improved the energy storage density of the ceramics.When x=0.06 and the sintering condition is 1100℃for 3h,the effective energy storage density W_rec reaches 1.600 J/cm³,and the energy storage efficiencyηis 67.0%.The dielectric temperature spectrum shows that with the increase of AgNbO₃ content,the two abnormal peak regions of the ceramic are gentle,indicating that the temperature stability of the ceramic energy storage is improved.（1-x）[0.94(Bi_0.535Na_0.465)TiO₃-0.06Ba TiO₃]-x Sr TiO₃（BNT-BT-ST）lead-free ceramics with pure perovskite structure were prepared by solid-state sintering.SEM test shows that the addition of ST can effectively inhibit the average grain size and improve the breakdown resistance field strength,and the breakdown resistance field strength reaches the maximum at x=0.2,up to E_b=14 k V/mm.The dielectric test shows that the dielectric constant of ceramics at room temperature increases fromε_r=1000 toε_r=3500 with the increase of ST content.And with the increase of x value,both peak T_sand Tm are moving towards the lower temperature direction.All the results show that the addition of ST improves the energy storage performance of ceramics.The optimal energy storage performance group was divided into x=0.2,effective energy storage density was about W_rec=1.664 J/cm³,and energy storage efficiency was aboutη=53%.