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

为了研制一种能在强电场下进行测量的粉末x射线衍射仪，分析钙钛矿型铁电材料在强电场作用下的结构变化，测量了NbN镁铅和PZT陶瓷在1.5KV/mm电场下的X射线衍射强度和衍射角。根据电场感生应变和压电常数的实验结果，分析了测量的衍射强度和衍射角随电场的变化。PZT的晶格应变与陶瓷的电致伸缩应变常数基本一致。在PZT中，h00和001衍射角的强度变化代替了衍射角的变化。强度的变化表明，PZT中发生了铁电90度磁畴的重定向。发现PZT的电场感应应变是由于压电效应引起的应变和高电场下铁电90度磁畴重新取向的应变之和。

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.