Raman-spectroscopic investigation of image and image perovskites

Raman spectroscopy was employed to investigate the structures and phonon modes of image and image ceramics. It was found that Ba-based samples belong to the tetragonal image (#128 or image space group, while Sr-based materials belong to the monoclinic image (#14 or image space group. Low-temperature measurements did not show any phase transition down to 77 K. Lorentzian lines were used to fit the experimental data, which presented 14 phonon modes for image and 24 modes for image, in perfect agreement with the theoretical factor-group analyses for the proposed structures. This paper reports, for the first time, a tetragonal image structure for an indium-containing perovskite material.