Bi2(Sn0.95Cr0.05)2O7: Structure, IR spectra, and dielectric properties

Infrared absorption spectra of the bismuth pyrostannate Bi2(Sn0.95Cr0.05)2O7 were investigated in the frequency range 350−1100 cm−1 at temperatures of 110−525 K. Four frequency regions with split absorption lines are distinguished. Softening of frequencies at the structural transitions was observed. The maxima of permittivity measured in the frequency range 1−200 kHz at temperatures 100−400 K were determined. It was found that the magnetic susceptibility changes its sign in the low-temperature region. The correlation between anomalies in the magnetic susceptibility, permittivity, and absorption line intensity was established. Softening of frequencies is explained by the variation in the coefficient of thermal expansion of the lattice. The temperature behavior of permittivity is described using the Debye model.