LASER-INDUCED CRYSTALLIZATION OF GLASSY CESIUM METABORATE STUDIED BY RAMAN-SPECTROSCOPY

The Raman spectra of crystalline and amorphous solids with the caesium metaborate composition reveal that while the former consists solely of BØ2O- units in ring metaborate arrangements, the latter contains a significant fraction of BØ4- tetrahedra as well (Ø,O: bridging and non-bridging oxygen atoms, respectively). The laser-induced crystallization of the glass, monitored in situ by Raman scattering, is found to proceed via the isomerization reaction: BØ4- ⇌BØ2O-. Kinetic data were obtained from the Raman spectra, at T = 200 ± 20°C, and indicate a Johnson-Mehl-Avrami time dependence of the crystallized volume, with a rate constant k = (1.2±0.1)×10-3s-1 and Avrami factor n = 1.8±0.1. © 1990.