Study of molybdenum coordination state and crystallization behavior in MoO3-La2O3-B2O3 glasses by Raman spectroscopy

The ternary MoO3-La2O3-B2O3 glasses containing a large amount of MoO3 (10-50 mol%) are prepared, and their structure and crystallization behavior are examined from the Raman scattering spectrum measurements and X-ray diffraction analyses. It is found that the glass transition and crystallization temperatures and the thermal stability against crystallization decrease with increasing MoO3 content. It is suggested that the main coordination state of Mo6+ ions in the glasses is isolated (MoO4)(2-) tetrahedral units giving strong Raman bands at 830-860 and 930 cm(-1). It is found that the crystalline phases in the crystallized glasses are mainly LaMoBO6 and LaB3O6, and the main crystallization mechanism in MoO3-La2O3-B2O3 glasses is surface crystallization. LaMoBO6 crystals are found to give strong Raman bands at 810-830 and 910 cm(-1). (C) 2011 Elsevier Ltd. All rights reserved.