Optical phonons in mixed sodium potassium tantalates
Optical phonons in mixed sodium potassium tantalates
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混合钽酸钾钠中的光学声子
DOI：
10.1103/physrev.183.595
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发表时间：
1969
期刊：
影响因子：
--
通讯作者：
U. Höchli
中科院分区：
文献类型：
--
作者：
M. Maglione;S. Rod;U. Höchli
研究了混晶系统${\mathrm{Na}}_{x}{\mathrm{K}}_{1\ensuremath{-}x}\mathrm{Ta}{\mathrm{O}}_{3}$的成员在4~6 0 0℃，x=0.0，0.12，0.40，0.6 5和0.85℃时的红外和拉曼光谱。红外数据表明，低频声子是“软模”，是铁电相变的原因。模的温度依赖关系与介电行为相关联，与目前的位移铁电体理论相一致。在顺电相，拉曼光谱完全是二级的，并且与阳离子浓度无关。在铁电相中观察到了一级拉曼光谱，表明铁电相为{C}{4V}$结构。推导了布里渊区中心和边界光学模式的频率随温度和成分的变化关系。
The infrared and Raman spectra of members of the mixed-crystal system ${\mathrm{Na}}_{x}{\mathrm{K}}_{1\ensuremath{-}x}\mathrm{Ta}{\mathrm{O}}_{3}$ have been studied at temperatures from 4 to 600\ifmmode^\circ\else\textdegree\fi{}K for $x=0.0,0.12,0.40,0.65, \mathrm{and} 0.85$. The infrared data indicate that the low-frequency phonons are "soft" modes and are responsible for the ferroelectric phase change. The temperature dependence of the modes has been correlated with the dielectric behavior and is in agreement with current theories of displacive ferroelectrics. In the paraelectric phase, the Raman spectrum is entirely second order and qualitatively independent of cation concentration. First-order Raman bands are observed in the ferroelectric phase for $xl0.70$ and a ${C}_{4v}$ structure is strongly indicated. The frequencies of the optical modes at the center and at the boundary of the Brillouin zone have been deduced as a function of temperature and composition.