Investigations On The Energy Storage And Electrocaloric Properties In Lanthanum Lead Zirconate Stannate Antiferroelectric Ceramics

In this thesis,lead zirconate stannate antiferroelectric material was chosen as the research object,bulk ceramics and thick film ceramics were prepared using the conventional solid-state reaction and tape-casting approaches,respectively.The energy storage characteristics,electrocaloic effect and phase transition behaviors of the bulk ceramics were investigated.The results done in this thesis are summarized as follows,(1)The(Pb0.998La0.02)(ZrxSn1-x)0.995O3(PLZS)antiferroelectric bulk ceramics were prepared using a solid-state reaction method.The results show that the doping of Zr4+ can reduce the antiferroelectric(AFE)-ferroelectric(FE)phase transition electric field and increase the polarization intensity.The permittivity as a function of temperature shows a broad peak,which may be due to the compositional inhomogeneity caused by the randomly distributed tin and zirconium ions,which resulting in the multicell cubic phase.At room temperature,the dielectric loss is small,which is conducive to its applications at high electric fields.The P-E hysteresis loops were procured at different temperatures.At room temperature,the recoverable energy density(Wrec)of the bulk ceramics with 0.6 mol%zirconium ions was 4.8 J cm-3,and the energy efficiency was 82.5%.A large negative electrocaloric effect(ΔT=-10.2 K)was obtained at 3 83 K and 20 MV m-1 by calculating the adiabatic temperature change in terms of the Maxwell relation.Finally,the charge/discharge P-E loops were fitted and the relationship between the charge-discharge energy and the electric field for normal ferroelectrics,relaxor ferroelectrics and antiferroelectrics were discussed,and a criterion was procured,i.e.,the discharged energy density as a function of applied electric field fits for the equation,i.e.,Wd～En,n>2 for PZT based antiferroelectrics;n<2 for normal ferroelectrics,relaxor ferroelectrics,and AgNbO3 series antiferroelectrics.(2)The thick film ceramics(Pb0.998La0.02)(ZrxSn1-x)0.995O3 were prepared using the tapecasting method and two-step sintering process.SEM observation showed that the grain structure was dense,and the thickness of the crioss-section area was about 50 μm.The maximum breakdown electric field of the thick film ceramics(Pb0.998 La0.02)(Zr0.55Sn0.45)0.995O3 at room temperature is 52 MV/m,the energy storage density is 13.6 J/cm3 for charge,the energy storage density is 11.74 J/cm3 for discharge,and the energy storage efficiency is 86.3%.The relationship between the phase transition behavior and temperature at high electric fields was discussed.When the temperature is low,the phase transition behavior of antiferroelectric is AFE-FEⅠ-FEⅡ,and when the temperature is high,the phase transition of antiferroelectric directly becomes AFE-FEⅡ,passing over the FEⅠ phase.(3)PLZS bulk ceramics with different lanthanum contents were prepared by changing the doped lanthanum content of 0.02 mol%,0.04 mol%,0.06 mol%and 0.08 mol%,and the effect of La3+ content on the energy storage performance of PLZS bulk ceramics was studied.The grain size decreases with the increasing lanthanum ionic content.It was found that with the increasing lanthanum content,the dielectric breakdown electric field of PLZS ceramics increases gradually,and the polarization decreases gradually.When the content of lanthanum ion is 0.06,the ceramic sample has a very high energy storage efficiency.At this time,the discharge energy storage density is 3.5 J/cm~3,and the energy storage efficiency is up to 92.1%.