Phonon spectra of CBN crystals

The room temperature phonon modes of both the alkali metal doped and pure CBN (CaxBa1−xNb2O6) crystals were determined using the Raman scattering technique. Owing to the intrinsic disorder of the tetragonal lattice we observe few and broad bands. The wavenumber of the internal modes observed shifts upwards when the volume of the unit cell increases. This blue shift is likely to be related to the closer packing of the NbO6 octahedrons. The Curie temperatures of the ferroelectric to paraelectric phase transition for the CBN-like crystals were obtained from DSC measurements. The Raman spectra of CBN32 in the temperature range from 300 to 568 K were also recorded in order to investigate the phase transformation.