钛酸锶钡材料在外加电场作用下的拉曼光谱研究

采用传统的固相反应烧结方法制 备Ba_xSr_1-xTiO₃（0.40≤ x ≤0.70）陶瓷，借助于Raman散射光谱，研究了陶瓷样品在不同原位电场作用下Raman振动模式的变化，观察到居里温度附近显著的电场诱导的四方–立方相之间的转变. 结果表明A₁（TO₃）和E（TO₄）两种振动模式与晶体的结构存在密切的联系，这两种模式源于O-Ti-O沿晶格中c轴的方向和ab面内的振动. A₁（TO₃）/E（TO₄）之间Raman峰的相对强度比，随外加场强的增加明显升高，顺电相逐渐转变为铁电相，晶格的畸变越来越明显，其宏观性能上表现为介电常数的降低，可调率的增加. 同时对居里温度附近电场诱导的结构相变对顺电相下介电非线性的贡献进行了探讨.关键词：钛酸锶钡Raman散射光谱结构相变

Raman spectra studies on (Ba,Sr)TiO3 ceramics under dc electric fields

Ba_xSr_1-xTiO₃ (0.40≤x≤0.70) ceramics have been prepared by the conventional solid-state reaction method. The changes of vibration modes in the pure Ba_xSr_1-xTiO₃ system have been investigated for an in-situ electric field by Raman spectra, and the transition from the cubic phase to tetragonal phases were obviously observed near the Curie temperature (T_c). Detailed results indicate that the A₁(TO₃) and E(TO₄) modes correspond to the vibrations of O-Ti-O bond along a-axis in the ab plane, which are strongly related to the lattice structure of ABO₃. With increasing electric field, the intensity of A₁(TO₃)/E(TO₄) ratio is increased, suggesting that more and more paraelectric states are transformed into ferroelectric states, thus leading to the deformation of lattice, which results in the decrease of dielectric constant and the increase of tunability. The electric-induced-structure phase transitions responsible for the nonlinear dielectric properties are also discussed.
Keywords：barium strontium titanateRaman spectrastructure phase transitions