本文采用拉曼散射技术在温度从374到-196℃的范围内, 研究了弛豫型铁电单晶0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3(PMNT)。观察了在不同温度下拉曼光谱的变化, 经分析这些变化反映了该晶体经历了两个相变: 第一个相变温度发生在120℃, 从顺电立方相到铁电四方相的相变, 780 cm-1处模式在VH偏振下的改变标志了这一相变; 第二个相变温度发生在34℃, 是从铁电四方相到铁电三方相的相变, 软模的出现代表了这一相变。

Ferroelectric relaxor 0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3(PMNT) single crystal in a wide temperature range from 374 to -196℃ were studied using Raman scattering techniques. The change of the Raman spectral revealed the existence of two structural phase transitions. The first one, from the cubic to tetragonal phase at 120℃, This is verified by the mode of 780 cm-1 measured in VH polarization. The second one, from the tetragonal to rhombohedral phase, occurs at about 34℃. The new A1 mode gives us a useful identifier for this phase change.