Phase Transitions In High-Strain (111)-Cut Pb(Mg1/3Nb2/3)0.7Ti0.3O3 Crystal

• Main Authors: Chuang Hui-Tsung, 莊惠宗
• Other Authors: Tu Chi-Shun
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/07481749275774994880

碩士 === 輔仁大學 === 物理學系 === 96 === Abstract Phase transformations of the (111)-cut Pb(Mg1/3Nb2/3)0.70Ti0.30O3 single crystals before and after an electric E-field poling have been investigated by means of dielectric permittivity, hysteresis loop, polarization current, and in situ x-ray diffraction as a function of temperature. An R-T-C transition sequence was observed in the unpoled sample upon zero-field heating. R, T, and C are rhombohedral, tetragonal, and cubic phases, respectively. After a prior E-field poling, an extra intermediate monoclinic (possible MA) phase was induced and the crystal underwent an R-MA-T-C phase sequence with significant responses in polarization current. The dielectric dispersion was diminished after poling and reappeared in the cubic state. The dielectric permittivities with and without a prior poling were found to follow the Curie-Weiss equation, =C/(T-To), above the Burns temperature 505 K with the same Curie-Weiss constant C=1.9´105 K and Curie-Weiss temperature To=460 K.