Relation between material property and crystal structure of perovskite ferroelectrics under high electric field

本研究的目的是开发一种能够在高电场下测量的粉末x射线衍射仪，研究了钙钛矿型铁电体在高电场下的结构变化，测量了镁酸铅（PMN）和锆钛酸铅（PZT）陶瓷在高电场下的X射线衍射强度和衍射角，并与未加电场的样品进行了比较。结合电场诱导应变和压电常数的实验结果，分析了衍射强度和衍射角随电场的变化，指出电场诱导衍射角的变化，即晶格的应变，在高电场作用下，PMN的晶格应变与陶瓷的电致伸缩应变常数基本一致，而PZT的晶格应变与陶瓷的电致伸缩应变常数基本一致，用h00和001衍射峰强度的变化代替衍射角的变化，强度的变化表明，结果表明，PZT的电场诱导应变是压电效应引起的应变和高电场下铁电90度畴重取向引起的应变之和。

The purpose of the present study was to develop a powder x-ray diffractometer which was capable of measuring under a high electric field, and to analyze structural changes in perovskite ferroelectrics under a high electric field.The x-ray diffraction intensities and diffraction angles of lead magnesium niobate(PMN)and lead ziconate titanate(PZT)ceramics were measured under the electric field up to 1.5kV/mm.The diffraction intensities and diffraction angles measured as a function of electric filed were analyzed with respect to the experimental results of electric field induced strain and piezoeiectric constant.The electric field induced change of diffraction angles, that is the strain of crystal lattice, were detected in PMN under a high electric field.The strain of crystal lattice was approximately consistent with the electrostrictive strain constant of ceramics.In the case of PZT,the change in the intensities of h00 and 001 diffractions were detected in place of diffraction angles.The change of intensities indicated that the reoriantation of ferroelectric 90 degree domains took place in the specemen.It was found that the electric field induced strain of PZT was the sum of the strain due to the piezoelectric effect and the strain due to the reorientation of ferroelectric 90 degree domains under a high electric field.