Raman study of phonons in K2Al2B2O7 crystals

Abstract

A Raman scattering study of the vibrational modes in K 2 Al 2 B 2 O 7 crystals has been performed at room temperature. The vibrational modes are classified by the nuclear site group analysis method and the internal vibrational modes are assigned to vibrations of the BO 3 triangle and AlO 4 tetrahedron.

Incommensurate structure of Ca2Al2O5 at high temperatures – structure investigation and Raman spectroscopy

“…Calcium ferrite-type CaAl 2 O 4 is built up of double chains of edge-shared AlO 6 octahedra in contrast to Ca 2 Al 2 O 5 at room temperature, where layers of AlO 6 octahedra and zweier single chains of AlO 4 tetrahedra are the main building units (Kahlenberg et al, 2000). A Raman study of K 2 Al 2 B 2 O 7 (Hu et al, 2004) (Kahlenberg et al, 2007) show very similar spectra with intense bands around 900-1100 and 450-700 cm À1 , related to SiO 4 tetrahedra stretching and bending vibrations. The higher wavenumber can be explained by the stronger bonding and shorter interatomic distances of Si-O compared with Al-O.…”

Spectroscopic study of red-light-emitting centers in K2Al2B2O7: Fe single crystals

“…4) dominates above 20 K and determines the PL emission spectrum at 25 K (Fig. 3) ), which is caused by the external vibrations originating from the translational motions of K ion and anion group plus the librational motion of the anion group [57]. In this connection, the thermal quenching of R-luminescence can be attributed to the electron-phonon interaction in the appropriate Al 2 O 7 cluster.…”

High-resolution temperature-dependent Brillouin scattering studies of ferroelectricK3Nb3O6(BMączka1, Hanuza2, Kojima3 2008Phys. Rev. B

“…Since our studies show very clear critical slowing down of the depolarized CP near T 4 , it is very likely that instability of the AЉ mode triggers the transition at T 4 and the symmetry decreases to C 1 . If this is the case, the e 4 spontaneous strain should appear below T 4 also expected if the phase transition occurs from C s into C 2v symmetry. Our results show that, indeed, a clear anomaly of the c 44 is observed at T 4 .…”