Raman investigation of vibrational states in quartz-type GaPO4 at various temperatures
✍ Scribed by J.-P. Pinan-Lucarre; R. Ouillon; P. Ranson
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 154 KB
- Volume
- 29
- Category
- Article
- ISSN
- 0377-0486
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✦ Synopsis
The Raman-active lattice modes in quartz-homeotypic crystal at low and room temperature were investi-GaPO 4 gated using a Raman spectrometer of limiting resolution 0.005 cm-1. Particular attention was paid to the comparison of the LO-TO splittings of the low-lying energy E modes in the series and The a-SiO 2 , a-AlPO 4 GaPO 4 . linewidths and Raman shifts of the (ca. 460 cm-1) and E (TO) (ca. 117 cm-1) modes in were measured A 1 GaPO 4 in the temperature range 8-300 K. These data were compared with those obtained for a-quartz and berlinite for the corresponding and E modes. The phonon dampings are discussed in terms of simple cubic and (a-AlPO 4 ) A 1 quartic anharmonic processes. In particular, a dephasing process involving two acoustic phonons of mean wavenumber ca. 60 cm-1 was assumed. The residual linewidths at T Ç 0 K are interpreted in terms of a random distribution of impurity sites in the crystal.