Electromechanical Coupling Performance of (111)-Oriented 0.7PMN-0.3PT Thin Film

Abstract

Abstract: Due to its excellent physical properties, ferroelectric thin films are widely used in the fields of microelectronics, optoelectronics, and microelectromechanics. In terms of theoretical research on ferroelectric thin films, the phenomenological theory of thermodynamics can effectively predict the phase structure, polarization characteristics and electromechanical properties of ferroelectric thin films, and has been well applied in the research of (001)-oriented ferroelectric thin films. However, there are very few research reports on (111)-oriented ferroelectric thin films. Therefore, the thermodynamic potential energy function and the calculation method of electromechanical properties of the (111)-oriented thin film by transforming order parameters of the system was constructed in this paper. Based on constructed theory, the phase structure and electromechanical properties of (111)-oriented 0.7PMN-0.3PT ferroelectric thin film were studied. The results reveal that the phase structures of the (111)-oriented 0.7PMN-0.3PT ferroelectric thin film mainly have three symmetrical phases with interchangeable polarizations along the crystal axis, they are paraelectric phase PE, rhombohedral phase R and monoclinic phase M_A (or M_B). By the controling of misfit strain and external electric field, the (111)-oriented 0.7PMN-0.3PT thin film exhibits excellent electromechanical properties. At the boundary of the R-M_A phase transformation, the dielectric constants ε11, ε22, ε33 and the out-of-plane piezoelectric coefficient d33 have achieved a maximum value. With the external electric field E₃=0, 50 kV/cm, 100 kV/cm and 200 kV/cm, the peak values of the out-of-plane dielectric constant ε33 are 4 382, 2 646, 2 102 and 1 600, respectively, and the peak values of the out-of-plane piezoelectric coefficient d33 are 303.8 pm/V, 241.9 pm/V, 219.7 pm/V and 195.1 pm/V. The misfit strain and external electric field can better control the electromechanical coupling performance of the film, which provide a reference for the preparation of devices with excellent electromechanical coupling performance.

Key words: lead magnesium niobium titanate, ferroelectric thin film, (111)-orientation, phase structure, thermodynamic theory, piezoelectric coefficient, dielectric constant

CLC Number:

TB383

LI Qiang, ZHANG Peizhi, LYU Jinbin, ZHANG Qingyong, LIU Li, YE Yang. Electromechanical Coupling Performance of (111)-Oriented 0.7PMN-0.3PT Thin Film[J]. JOURNAL OF SYNTHETIC CRYSTALS, 2022, 51(1): 112-119.

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