Investigations On The Preparation And Energy Storage And Electrocaloric Effect Properties In Lead Zirconate Titanate-based Thick Film Ceramics

Ferroelectrics and antiferroelectrics play an important role in energy storage,electrocaloric effect and relevant research areas.Since lead zirconate titanate based thick film ceramics have a higher breakdown electric field than their bulk ceramics,the thick film ceramics were prepared and the properties of energy storage density were studied in this thesis.Because of the good features of lead stannate in thermodynamics and dynamics,Sn⁴⁺ions were added into the PLZT ceramics to improve the energy storage density and electrocaloric effect in terms of forming the PLZST and PLZS thick film ceramics with higher tin contents.Firstly,the PZT ceramic powders were synthesized via a solid-state reaction,and green thick films were obtained by a tape-casting process.After sintered,Pb Zr_1-xTi_xO₃（x=0.45,0.48,0.50,0.55）thick film ceramics（thickness of 50μm）with different Ti⁴⁺contents were procured.The influence of Ti⁴⁺ionic content in Pb Zr_1-xTi_xO₃on the ferroelectric and dielectric properties were studied.The energy storage density under different electric fields and temperatures were calculated pursuant to the polarization–electric field hysteresis loops.The results indicated that when Ti⁴⁺ionic content is near48 mol%（at the morphology phase boundary（MPB））,the thick film ceramics have the maximum polarization and dielectric constant.The maximum energy storage density is1.79 J/cm³at 24 MV/m for Pb Zr_0.45Ti_0.55O₃thick film ceramics.Secondly,for Sn⁴⁺ionic incorporation with the PZT system,Pb_0.97La_0.02(Zr_0.46-xSn_0.54Ti_x)O₃（x=0.04,0.06,0.08,0.15,0.18）thick film ceramics were prepared using the tape-casting process.The effects of Ti⁴⁺ionic content on the polarization and dielectric properties of thick film ceramics were investigated.The results indicate that the thick film ceramics with low Ti⁴⁺mol%content were antiferroelectric phase,the decrease of Ti⁴⁺ionic content is beneficial to the stability of antiferroelectric phase and the decrease of dielectric constant.When the Ti⁴⁺ionic content was increased to 15mol%and 18 mol%,the thick film ceramics changed from antiferroelectric phase to ferroelectric phase.Pb_0.97La_0.02(Zr_0.46-xSn_0.54Ti_x)O₃thick film ceramics can withstand a high electric field of 60 MV/m,the maximum energy storage density is 5.2 J/cm³,and the energy storage efficiency is 78%.The electrocaloric effect was calculated based on the Maxwell relation,and the adiabatic temperature changeΔT_max=2.47℃was procured near the Curie temperature.Finally,the system Pb_0.97La_0.02(Zr_1-xSn_x)O₃（PLZS）（x=0.30,0.35,0.40,0.45,0.50）thick film ceramics were prepared,and the effect of Sn⁴⁺ions on the polarization and electric field at which the antiferroelectric phase was converted into ferroelectric phase(E_AFE-FE)was studied.The FE（I）phase in Pb_0.97La_0.02(Zr_0.50Sn_0.50)O₃thick film ceramics was investigated in detail.The FE（I）phase existed at temperature lower than 70℃,and the lower the temperature,the more stable the FE（I）phase.At room temperature,the transition electric fields of AFE-FE（I）and FE（I）-FE（II）phase are 23 MV/m and 32.2MV/m respectively,and the lower the temperature,the higher the transition electric field.The maximum energy storage density of Pb_0.97La_0.02(Zr_0.50Sn_0.50)O₃thick film ceramics obtained is 8.9 J/cm³,and the energy storage efficiency is 86%.At 90℃,the energy storage efficiency can reach 93.3%.In addition,the electrocaloric effect of Pb_0.97La_0.02(Zr_0.50Sn_0.50)O₃thick film ceramics was calculated according to the Maxwell relation.The calculated temperature change valueΔT_max=-9.8℃at 26 MV/m,indicating that the PLZS thick film ceramic shows a significant negative electrocaloric effect.