L. X. Li

RAMAN SCATTERING INVESTIGATIONS IN PRXY1-XAL3(BO3)4 SINGLE CRYSTALS

The crystal growth, structure and Raman spectra of the PrxY1−xAl3(BO3)4 (PYAB) single crystals are introduced. The experiments show that the characteristic lattice vibrational spectrum of the PYAB arises mainly from the internal vibrations of the BO3 and AlO6 groups, and that the rigidity of the lattice is mainly ascribed to the vibrations of B—O and Al—O bonds. For the Pr/YO6 groups, there is no O2− ion that is independent of the BO3 and AlO6 groups, and no new internal vibrational mode arises. Hence the characteristic lattice vibrational spectrum is not affected by the rare earth ions doped in the PYAB, and the ions can affect the external vibrations of the BO3 and AlO6 groups and improve the structural and optical quality of the crystals. Copyright

Structure and the nonlinearity of lithium triborate studied by Raman and infrared reflectivity spectroscopy

Raman and infrared measurements of the LiB 3 O 5 (LBO) crystals were completed. The experimental results shown here are more and stronger Raman lines and infrared absorption peaks, which implies that the external vibrations of the trigonal (BO 3 ) 3− and tetrahedral (BO 4 ) 5− ions, especially the former, in the six-membered boron–oxygen rings at the low wave number are strong and the internal vibrations of the (BO 4 ) 5− ions above 200 cm −1 are stronger than those of the (BO 3 ) 3− ions if compared with the Raman spectra of BaB 2 O 4 crystals. These are caused due to the slope and distortions of the B 3 O 7 rings and their BO 3 and BO 4 units in LBO, which change the structural rigidity of the crystals, intensify the long-range electrostatic force and short-range molecular force, and shorten the ultraviolet absorption edge.

Soft-Mode Spectroscopy in Fe:KTa1-xNbxO3 Crystals

Fe-doped potassium tantalite niobate, Fe:KTa 1-x Nb x O 3 (Fe:KTN), crystallizes with x = 0.48 and a perovskite-type structure in tetragonal system with point group 4mm, conforming space group P4mm. The paraelectric-ferroelectric structural transition of the Fe:KTN is studied by Raman scattering investigations. A condensed soft lattice vibrational mode at the phase transition has been analyzed. It originates from the symmetric O2/O3-Nb/Ta-O3/O2 in-plane bending of the Nb/TaO 6 group. The soft optical phonon mode concerns the extraordinary transverse optical phonons propagating along the [110] direction. The Raman spectra measured reflect the crystal disorder. Curie temperature measured by two methods is within 353 and 3 56.5 K.

The inelastic light Scattering of RbTiOPO4 single crystal

Abstract This paper reports the determination of the polarized Raman spectra of the nonlinear crystal, rubidium titanium oxide phosphate (RTP). Comparing the Raman spectra of RTP with that of potassium titanium oxide phosphate (KTP), we have found that different central ions cause slight shifts of frequency, and the PO4 tetrahedrons and TiO6 octahedrons play the important role in Raman Scattering.

Phase transition and the soft lattice mode of a perovskite crystal studied by Raman scattering and thermal measurements

The paraelectric–ferroelectric structural transition of potassium lithium tantalite niobate has been studied by both Raman scattering and thermal measurements. A condensed soft lattice vibrational mode at the phase transition has been analyzed. It originates from the symmetric O2/O3–Nb/Ta–O3/O2 in-plane bending of the Nb/TaO 6 group. The soft optical phonon mode concerns the extraordinary transverse optical phonons propagating along the [1 1 0] direction. The thermal expansion experiments show a displacive phase transition and a big thermal contraction in the c direction of the crystal, with an average linear expansion coefficient α c = −4.52 × 10 −5 K −1 . The phase transition temperature and enthalpy are 358 K and 0.50 J/g, respectively. Curie temperature measured by four methods is within 353 and 360 K.