Raman spectroscopic study of ceramic Sr₂Bi₄Ti₅O₁₈

Raman spectra of ceramic Sr₂Bi₄Ti₅O₁₈ (SBTi5) are reported to consist of four different Raman bands.Temperature-dependent spectra reveal the relationship between the lattice vibration and the material's structure. There appears a relatively large change in structure of the material at about 273K.The anharmonic potential of the material has a great influence on its phonon mode full width at half maximum (FWHM), which can be expressed by a function of temperature. Theoretical fittings of the FWHMs for the two modes at around 312 cm^-1 and 464 cm^-1 indicate that the latter phonon mode is more anharmonic than the former one.