Investigation On Material Design,Preparation And Energy Storage Characteristics Of Lead-based Antiferroelectric With High Energy Storage Density

The improvement of dielectric energy storage performance is of great significance for the further application of pulse power technology.As a member of the energy storage medium,PbZrO3(PZ)based anti ferroelectric ceramics have attracted much attention in the current energy storage research field due to their high energy storage and charge-discharge performance.The excellent properties of PZ-based antiferroelectric ceramics are closely related to the field-induced phase transition.However,in previous studies,the revelation of the correlation between the above two is relatively weak.Especially,in order to meet the higher demand for dielectric energy storage under the current situation,and to further optimize the energy storage performance of PZ-based ceramics,it is particularly urgent and important to carry out deeper research on the correlation between the energy storage performance and the field-induced phase transition of antiferroelectric ceramics.Therefore,in view of the above problems,this paper studies the energy storage properties of PZ-based antiferroelectric ceramics with square-like,multiphase transition and slender-like hysteresis loops respectively through reasonable composition design,reveals the characteristics of field-induced phase transition of these three types of antiferroelectric,and clarifies the correlation between the energy storage performance and field-induced phase transition of antiferroelectric ceramics.The main research contents and results are as follows:The critical electric field of antiferroelectric-ferroelectric phase transition of pure PZ ceramics(square-like)at room temperature is about 280 kV/cm,the breakdown field strength is 300 kV/cm,and the saturation polarization is about 54 μC/cm2,its energy storage density can reach 10.06 J/cm3 and the energy storage efficiency is 70.90%.The low energy storage efficiency of pure PZ ceramics is related to the large hysteresis width.The in-situ electric field Raman spectra of pure PZ ceramics show that the characteristic vibration of the antiferroelectric state(Pbam)is located at-52 cm-1,and the characteristic vibration of the ferroelectric state(Cm2m)appears near 412 and 637 cm-1;On the eve of phase transition,the change of lead ion order is not obvious,the shift of Zr4+ and the tilt of BO6 octahedron decreases;After the phase transition,the shift of Pb2+ and Zr4+ increases,the tilt of the BO6 octahedron further weakens.The high polarization of ferroelectric state is related to the large deviation of cations.The deviation of Zr4+ may cause the expansion of BO6 octahedron in the same direction and the contraction in the vertical direction.Compared with pure PZ,(Pb0.97La0.02)(Zr0.4+xSn0.6-x)O3(PLZS)system possesses the characteristics of electric field induced multi-step transition(antiferroelectricferroelectric Ⅰ-ferroelectric Ⅱ)(multiphase transition type).The optimal composition of PLZS matrix is an orthorhombic phase with a Zr/Sn ratio of 60/40.The breakdown strength of the ceramic is 430 kV/cm,the energy storage density is 11.66 J/cm3,the energy storage efficiency is 79.81%,and the discharge energy density is 8.78 J/cm3.Compared with the tetragonal structure,the crystal cells of the orthorhombic PLZS show greater distortion.The high polarization strength of the orthorhombic phase mainly comes from the cation displacement rather than the tilt of the BO6 octahedron,which is the origin of the optimal composition of the highest energy storage performance.The substitution of Sn4+can enhance the ferroelectricity and antiferroelectricity of the ceramic at the same time,which may induce the symmetry recovery of the matrix.The intermediate-temperature phase(AFE2)of PLZS system is an antiferroelectric phase with the same symmetry as the room temperature,and its characteristic vibration is the same as a part of the room-temperature phase.The ferroelectric Ⅰ state of the orthorhombic matrix is consistent with the ferroelectric Ⅱstate(R3c)of the tetragonal phase;The first phase transition of tetragonal matrix is mainly the extension of BO6 octahedral chains;The ferroelectric Ⅱ state of the orthorhombic phase is Cm2m phase.PLZS ceramics show very high energy storage density and high energy storage efficiency,which is a better matrix for energy storage.Especially,Ba2+doping can further optimize the energy storage performance.The optimum content of Ba2+is 2%mole,the breakdown strength of the ceramic is 450 kV/cm,the energy storage density can reach～12.80 J/cm3,the energy storage efficiency is～84.20%,the peak discharge current density exceeds 1800 A/cm2 and the peak discharge power density exceeds 320 MW/cm3.The increase of breakdown strength is the result of the interaction of ceramic microstructure and conductivity mechanism.The room-temperature phase(AFE1)of PLZS matrix is the coexistence of Pbam and Bmm2.Ba2+substitution improves the relative content of Bmm2 phase in the ceramic by reducing the phase transition temperature,thereby optimizing the energy storage efficiency of ceramics.The origin of ferroelectric Ⅱ state is different from that of ferroelectric Ⅰ.The electric field induced multi-step phase transition can be decomposed into the Bmm2-R3c phase transition and the subsequent Pbam-Cm2m phase transition.The polarization response of the Bmm2 phase is dispersive to the electric field.The optimization of Ba2+doping on the energy storage efficiency of the matrix is very limited.In contrast,the introduction of the second phase AgNbO3(AN)can significantly improve the energy storage efficiency and charge-discharge performance of the PLZS matrix.When the amount of AN is only 1%mole(AN1),the energy storage efficiency of ceramics is obviously improved to 85.05%,the energy storage density can reach 10.81 J/cm3,and the discharge energy density is 8.72 J/cm3;The energy storage efficiency of AN3 or AN4 exceeds 90.00%,but due to the low breakdown strength,the energy storage density of ceramics is insufficient(～6.00 J/cm3);The peak discharge current density of AN1 and AN3 can exceed 3000 A/cm2,and the peak discharge power density of AN1 is 556 MW/cm3.The introduction of AN forced the expansion of PLZS cells,thereby reducing the phase transition electric field and phase transition temperature of the ceramic;The introduction of the high amount of AN endows the matrix with more Bmm2,the Pbam phase decreases or even disappears at room temperature;The temperature-induced phase transition of PLZS matrix is AFE1-AFE2-Multicell cubic phase-Paraelectric phase.The multicell cubic phase with linear hysteresis loop-like characteristics should be a macroscopic pseudo-cubic structure composed of the AFE2 phase and the paraelectric phase.For the incommensurate antiferroelectric phase with very high energy storage efficiency(slender type),its lower energy storage density is related to the lower phase transition electric field and breakdown strength.The enhancement of the phase transition electric field can be obtained by doping the high amount of La3+(6%mole)and the appropriate amount of Cd2+.The optimization of the breakdown strength can be achieved through the effect of the sintering additive Cd2+and the thinning effect on ceramics via the tape-casting method.The results show that when the content of Cd2+of the(Pb0.91-xCdxLa0.06)(Zr0.6Sn0.4)O3 system is 3%(Cd3),the breakdown strength of ceramics can reach 870 kV/cm.At this point,the saturation polarization of ceramics exceeds 40 μC/cm2,the energy storage density is up to～19.30 J/cm3,and the energy storage efficiency is～91.00%.Moreover,under the electric field of 780 kV/cm,the discharge energy density of Cd3 is 15.35 J/cm3;In 10000 cycles of cyclic testing,the energy storage density attenuation is less than 4%,and the energy storage efficiency is maintained at～95.00%,which is related to the smaller field-induced strain.The reversible switching features between the incommensurate antiferroelectric phase and the relaxor ferroelectric rhombohedral phase are the origin of high energy storage efficiency.The adjustability of the incommensurate phase energy storage efficiency is related to the adjustability of the incommensurate period.The different relaxor degrees of the ferroelectric phase affect the polarization electric field response of the matrix in the depolarization process.