INFRARED STUDIES OF PEROVSKITE TITANATES

摘要: The infrared reflection and transmission spectra of CaTi${\mathrm{O}}_{3}$, SrTi${\mathrm{O}}_{3}$, PbTi${\mathrm{O}}_{3}$ have been measured from 4000 to 30 ${\mathrm{cm}}^{\ensuremath{-}1}$ at room temperature. data analyzed by means a Kramers-Kronig method, which the frequencies normal optically active vibrations were derived in agreement with obtained spectra. Three observed for cubic SrTi${\mathrm{O}}_{3}$ as required group theory. However, case CaTi${\mathrm{O}}_{3}$ PbTi${\mathrm{O}}_{3}$, crystallize slightly distorted perovskite structures become orthorhombic tetragonal, respectively, additional bands found had not previously. These distortions ideal symmetry would split degenerate modes possibly give frequencies. results are compared those other workers. From presented two features emerge: (1) Two ${\ensuremath{\nu}}_{1}$ ${\ensuremath{\nu}}_{2}$ essentially constant these titanates independent cation. (2) vibration lowest frequency, ${\ensuremath{\nu}}_{3}$, is responsible ferroelectric behavior, appears decrease increasing cation mass. This suggests mode assignment proposed Last.