Comparative study of the rare earth environment in rare earth metaborate glass (REB3O6, RE=La, Nd) and in sodium borate glasses

• Published in: Journal of non-crystalline solids Vol. 425; pp. 91 - 102
• Main Authors: Majérus, O., Trégouët, H., Caurant, D., Pytalev, D.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.10.2015
• Subjects: Bearing; Borate glasses; Borates; Crystal structure; Glass; Glass structure; Neodymium; Optical spectroscopy; Rare earth metals; Rare earths; Sodium borates; Spectroscopy; Borate glasses; Optical spectroscopy; Glass structure; Rare earths
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/j.jnoncrysol.2015.05.031

The RE environment in the RE-metaborate glass (RE=La3+ or Nd3+) has been characterized by Nd LIII-edge EXAFS and Nd3+ and Eu3+ optical spectroscopy. The spectroscopic data have been compared with that of crystalline RE-metaborate and of two sodium borate glasses containing RE, a Na-poor borate glass (20mol% Na2O) bearing almost no NBOs (non-bridging oxygens), and a Na-rich borate glass (35mol% Na2O) bearing a significant number of NBOs. Spectroscopic data indicate that the RE–O ionicity and mean distance increase in the order Na-rich borate glass<RE-metaborate glass<Na-poor borate glass<RE-metaborate crystal. The distribution of RE3+ sites in the RE-metaborate glass is wider than in the two sodium borate glasses, as revealed by a larger RE–O distance distribution and larger inhomogeneous widths of optical transitions. Data are consistent with a model in which both NBOs and BOs take part to the coordination sphere of RE3+, like in the crystalline RE-metaborate phase, but they point out stronger RE3+–NBO bonds. The structural and bonding differences involving the RE3+ ions, between the glassy and crystalline forms of RE-metaborate, may be the basis of the high nucleation barrier observed in this congruent composition. •Nd3+ and Eu3+ optical spectroscopy and Nd LIII-edge EXAFS are used to study the RE3+ environment in REB3O6 glasses.•Stronger RE3+–NBO–B bonds in the REB3O6 glass than in the REB3O6 crystal are revealed.•Results for the RE3+ ions in the REB3O6 glass are compared with that of RE3+ in sodium borate glasses.•The RE3+ site is closer to inversion symmetry and has both BOs and NBOs.•The RE3+ distribution of sites is wider.