Pressure evolution of local structure and vibrational dynamics of the perovskite-type relaxor ferroelectric single crystal of 0.935(Na_0.5Bi_0.5)TiO₃-0.065BaTiO₃ (NBT-6.5BT) is systematically investigated via in situ Raman spectroscopy. The pressure dependence of phonon modes up to 30 GPa reveals two characteristic pressures: one is at around 4.6 GPa which corresponds to the rhombohedral-to-tetragonal phase transition, showing that the pressure strongly suppresses the coupling between the off-centered A- and B-site cations; the other structural transition involving the oxygen octahedral tilt and vibration occurs at pressure ∼13–15 GPa with certain degree of order-disorder transition, evidenced by the abnormal changes of intensity and FWHM in Raman spectrum.

通过原位系统研究了0.935(Na _0.5 Bi _0.5 )TiO ₃ -0.065BaTiO ₃ (NBT-6.5BT)钙钛矿型弛豫铁电单晶的局部结构压力演化和振动动力学拉曼光谱。高达 30 GPa 的声子模式的压力依赖性揭示了两个特征压力：一个在 4.6 GPa 左右，对应于菱面体到四方相变，表明压力强烈抑制了偏心 A 和 B 之间的耦合-位点阳离子；另一个涉及氧八面体倾斜和振动的结构转变发生在压力~13-15 GPa，具有一定程度的有序 - 无序转变，拉曼光谱中强度和FWHM的异常变化证明了这一点。