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Mossbauer spectra were taken of barium ferrite at temperatures ranging from 15K to 733K. The hyperfine parameters H,δ, f for ferric ions as function of temperature at different lattice sites were determined. Above 300K, the effective vibrating mass of the Mossbauer atom at the Fe(2) site Meff = 65±5 (in U) is larger than those at other sites, indicating a stronger covalent bonding with the neighbour oxygen atoms. We also discuss the temperature dependence of the unusually large quadrupole splitting due to ferric iron in the bipyramidal position, with a very small Mossbauer lattice temperature θM = 233±15 K.

Raman spectra of BaTiO3 and Ce: BaTiO3 single crystals have been recorded between room temperature and 180℃. Three new bands at 986,1204 and 1480 cm-1 in the X(ZZ) Y geometry are discovered. Based upon the temperature dependence of Raman scattering cross sections, the new bands are attributed to the second-order Raman spectra of BaTiO3, while the strong asymmetry bands at 275 and 514 cm-1 in A1(TO) spectrum are confirmed to be of first order. On the basis of above results, the Raman spectra of cubic BaTiO3 and the model of phase transitions are discussed. It is found that doping with Ce in BaTiO3 lowers its Curie temperature, which agrees with the experimental results of dielectric constants.

Polarized Raman spectra of all four symmetry species in single crystal LiB3O5 have been measured at room and high temperature. The vibrational modes are classified by the method factor group analysis and the internal vibration bands are tentatinely assigned to vibrations of BO3 triangle and BO4 tetrahedron. Based upon the experimental results of LO-TO splitting , the effective charges of polar modes and the static dielectric constants are calculated.

The Brillouin scattering tensers and the stiffening Christoffel equations in (100), (010), and (001) planes of C2v point group crystals are obtained at arbitery wave vector directions. Based on these results, all the independent elastic and piezoelectric constants of LBO crystals are determined by means of Brillouin scattering , and the sound velocity anisotropic curves in the three planes are also shown

In this paper, the Merten' s equation and dispersion relation of polaritons in the uniaxial crystal had been deduced from the generalized dispersion relation of the phonon-polariton. Raman spectra of every LO, TO mode and oblique phonons in BaTiO3 and Ce: BaTiO3 single crystals have been recorded, the directional dispersion curves are fitted on the basis of Merten's equation. Raman spectra of A1 polaritons with different wave-vector q have been measured and the high and low frequency dielectric constants in both BaTiO3 and Ce:BaTiO3 are calculated. Two broad asymmetry bands in A1(TO) Raman spectra and the mechanics of structure phase transition in BaTiO3 are also discussed. The influence of Ce on the structure of BaTiO3 single crystal are analysed.

Polarized Raman spectra of single crystal Li2B4O7 have been measured in the wavenum-ber shift range of 50-3000cm-1 at room temperature. The infrared absorption spectrum of Li2B4O7 has also been measured in the range of 200-4000cm-1 for powder samples dispersed in the pressed KBr disks. Based upon the experimental results of LO-TO splitting, the effective charge and mode strength of polar modes are calculated. A comparison of the structure and B-O stretching vibration frequency of various borate species suggests comparatively high nonlinear optical efficiency of Li2B4O7 crystals.

Under the condition of qc?ω, the generalized frequency dispersion relation of polar pho-nons is simplified- The generalized Kurosawa relation and LST relation are derived and verified by the Raman spectra of TGS singal crystal.

The crystal structure of tetragonal barium titanate (space group P 4 mm) was determined at 13.6℃, using the data collected by neutron four-circle diffractoraeter, R(F) = 0.0186. The O atoms near b sites distribute disorberly.