Raman spectroscopic study of structure of WO 3[sbnd]La 2O 3[sbnd]B 2O 3 glasses with no color and crystallization of LaBWO 6

Abstract

Glasses with the nominal compositions of xWO 3 25La 2O 3 (75 − x)B 2O 3 (mol%) with x = 15, 25, and 50 were prepared using a conventional melt quenching method, and their structure and crystallization behavior were examined from Raman scattering spectra and X-ray diffraction analyses. The glasses are colorless in the visible light region and give the optical band gap energy of 3.49–3.61 eV. The glass transition and crystallization temperatures and the thermal stability against crystallization decrease with increasing WO 3 content. The strong Raman bands at 840 and 940–960 cm −1 suggest that the main coordination state of W 6+ ions in the glasses is isolated (WO 4) 2− tetrahedral units. The formation of WO 6 octahedral units is also suggested in the glasses with high WO 3 contents. The main crystallization mechanism in the glasses is the surface crystallization, and the glass of 50WO 3 25La 2O 3 25B 2O 3 shows the crystallization of LaBWO 6 single phase. The present study proposes that WO 3 La 2O 3 B 2O 3 glasses and crystallized glasses are very interesting as optical functional materials.