Bi_(2-x)La_xTi_4O_(11)在静高压下的拉曼振动光谱及软模相变研究

A STUDY OF RAMAN SPECTRA AND THE SOFT MODE PHASE TRANSITION UNDER HYDROSTATIC PRESSURE IN Bi_(2-x)La_xTi_4O_(11)

本文测量了Bi_(1.8)La_(0.2)Ti_4O_(11)和Bi_(1.6)La_(0.4)Ti_4O_(11)在静高压下的拉曼振动谱,发现了软模的藕合模行为。通过比较Bi_2Ti_4O_(11)的热力学理论计算值和实验数据,确认这种耦合是软模和一个声学模间的耦合,发生的相变是一个由具有B_(?)对称性的带中心软光学声于驱动的二级铁弹相变。

The Raman spectra of Bi2-τLazTi4O11 under hydrostatic pressure have been completed. The behavior of the coupled soft mode is found. Through comparing the result of Bi2Ti4O11 obtained by thermodynamics with the experimental data, it is believed that the coupling is one between q≈0 soft optical phonon with B(?) symmetry and a acoustic phonon mode. The phase transition occurring in Bi2-zLazTi4O11 is a secondry order one driven by the soft mode.