Study On The Structure And Electrostrictive Effect Of CaZrO₃ Under High Pressure

Electrostriction is the elastic deformation phenomenon caused by ion polarization in dielectric materials under the action of electric field.There are few researches on electrostrictive materials under high pressure due to the limitation of high pressure experimental measurement methods and conditions of high pressure experimental equipment.In this paper,we systematically studied the structure and electrostrictive effect of CaZrO₃ under high pressure by means of synchrotron radiation X-ray diffraction and electrochemical impedance spectroscopy.The specific research results are as follows:(1)High-pressure synchrotron radiation X-ray diffraction results show that CaZrO₃ does not undergo a pressure-induced structural phase transition within the pressure range of 0-30.8 GPa,and all diffraction peaks move to high-angle directions.The intensity of the diffraction peaks decreases with the increase of pressure.The peak gradually widens as the pressure increases.(2)For the first time,the electrostrictive effect of CaZrO₃ material in the sealed sample cavity of DAC was measured by electrochemical impedance spectroscopy.The impedance spectroscopy considers detectable change tendency including m(=?I_F/?X)and b(=??/?E)instead of electrostrictive strain X as measured parameters.Both m and b are bigger than zero even for CaZrO₃ sealed in diamond anvil cell,resulting in that the electrostriction can be presented directly in form of inductive loop in the impedance spectra.(3)The corresponding equivalent circuit was selected to fit the impedance spectra of CaZrO₃ under high pressure.The fitting results are well fitted with the experimental results,indicating that the electrostrictive strain of CaZrO₃ is the state variable to be responsible for the generation of inductance.(4)From the fitting results,we can get the pressure dependences of inductance L and its reciprocal B.Herein,parameter B equals to the product of?I_F/?X and??/?E which can also be used as directly as the electrostrictive strain X to characterize the electrostrictive ability.Only those materials with B>0,i.e.with large electrostrictive effect,can generate inductance loop in the impedance spectra.(5)By analyzing the pressure dependence of the inductance L and its reciprocal B of the CaZrO₃ sample,it is found that the B value decreases linearly with the increase of pressure,indicating that the electrostrictive effect in CaZrO₃ is suppressed by pressure.By analyzing the characteristic relaxation frequency and time constant change graph with pressure,it is concluded that as the pressure increases,the characteristic relaxation frequency decreases and the time constant increases,which further proves that the electrostriction in CaZrO₃ has been suppressed by pressure.