Raman spectroscopic study of structure of WO3-La2O3-B2O3 glasses with no color and crystallization of LaBWO6

Glasses with the nominal compositions of xWO(3)-25La(2)O(3)-(75 - x)B2O3 (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 WO3 content. The strong Raman bands at 840 and 940-960 cm(-1) suggest that the main coordination state of W6+ ions in the glasses is isolated (WO4)(2-) tetrahedral units. The formation of WO6 octahedral units is also suggested in the glasses with high WO3 contents. The main crystallization mechanism in the glasses is the surface crystallization, and the glass of 50WO(3)-25La(2)O(3)-25B(2)O(3) shows the crystallization of LaBWO6 single phase. The present study proposes that WO3-La2O3-B2O3 glasses and crystallized glasses are very interesting as optical functional materials. (C) 2011 Elsevier B.V. All rights reserved.