锆钛酸铅多晶材料的F_R(LT)—F_R(HT)相变及其热释电性质

F_(R(LT))—F_(R(HT))TRANSITION AND PYROELECTRIC PROPERTIES OF RHOMBOHEDRAL LEAD ZIRCONATE—TITANATE POLYCRYSTALLINE

本文研究了用共沉淀技术制备的PZT四种菱方相组分的均匀单相多晶体的介电特性和热释电特性。实验发现。菱方—菱方相变点的极化强度的异常变化是材料组成的函数。从组成PZT90/10和PZT94/6多晶体样品上可观察到介电系数、极化强度和热释电系数随温度发生的异常变化。但对于菱方组分PZT60/40和70/30却只能观察到热释电性质的异常变化。该二组分多晶体的相转变温度范围十分宽。文中引进铁电唯象理论描述了F_(R(LT))—F_(R(HT))相变行为。

PZT polycrystalline with composition Pb(Zr_xTi_(1-x))0_3(0.6<x<0.95)undergoes a F_(R(LT))-F_(R(HT))phase transition.This kind ofmaterials has been extensively investigated for application as IRdetectors.In our studies,PZT homogeneous,single phase,ultrafinepowders with the composition of Pb(Zr_xTi_(1-x))0_3 were prepared bycoprecipitation technique.The dielectric properties and pyroelectricproperties were studied.It is known,from the measured data,thatthe step of polarization at F_(R(LT))-F_(R(HT))phase transition isvaried with composition.The anomalies of temperature dependenceof dielectric constant,pyroelectric properties can be observed forthe compositions of PZT 90/10 and PZT94/6.But for compositionsof PZT60/40 and PZT70/30,only the anomolies of temperature de-pendences of pyroelectric properties can be found.It can be specu-lated that the crystal structure is under no change,only the tilt ofoctahedral occurs.This addes an additional energy to the system.E_(R(LT))-F_(R(HT))phase transition is accompanied by the tilt ofoctahedral.The related free energy expression for this kind of tran-sition will be discussed in this paper.