SrBi_2Ta_2O_9纳米颗粒的Raman光谱研究

采用Raman光谱的方法研究了化学计量和非化学计量SrBi_2Ta_2O_9(SBT)纳米颗粒晶格振动行为.通过常温、变温Raman光谱分析,得到了SBT尺寸效应和结构对称性方面的信息.软模振子频率的平方随温度的变化不符合单一的ω_s~2=A(T_c-T)关系揭示了尺寸效应可以导致新的相变.非化学计量SBT的Raman振动峰强度改变和峰形变化的主要因素为总电荷数以及Sr与Bi原子之间的相互取代关系.单个分子式总电荷数低于化学计量SBT总电荷数的样品,总电荷数的因素起主要作用;总电荷数高于化学计量SBT的样品,Bi原子部分取代Sr原子位置为主要因素.

Study of Raman Spectra in SrBi_2Ta_2O_9 Nanoparticles

The lattice vibrations of stoichiometric and non-stoichiometric SrBi_2Ta_2O_9(SBT) nanoparticles were studied by Raman scattering method. The size effect and symmetrical characteristic were obtained by the Raman spectrum. In SBT nanoparticles, the square frequencies of soft mode as a function of temperature broke the relation of ω_s~2=A(T_c-T), which indicated a new phase-transition behavior driven by size effect. Compared with stoichiometric SBT nanoparticles, the intensity and location of vibration bands in nonstoichiometric samples were changed, which could be attributed to the variation of total charges of unit cell and substitution between Sr and Bi atoms. When the total charges of unit cell in non-stoichiometric sample is lower than that of stoichiometric one, the factor of total charges is dominated, and otherwise the substitution between Sr and Bi atoms play the major role.