The double role played by the Gd 2O 3 in the gadolinium–aluminum–borate–bismuthate quaternary glass forming tendency. GdBO 3 crystalline phase

Abstract

Glasses and glass–ceramics in the xGd 2O 3·(100 − x)[2Bi 2O 3·B 2O 3·Al 2O 3] system with x = 0, 1, 5, 10, 15, 20, 25, 30, 35, 50 mol% Gd 2O 3 have been prepared by the melt quenching method. The changes of the IR spectral features suggest that the formation of [BO 4] tetrahedra is reduced because the modified [BO 3] units containing one or more B–O–Gd bonds are unable to accept the fourth oxygen. Based on our results, we conclude that the accommodation of the networks with the excess of oxygen is possible by the deformation of Bi–O–Bi linkages, the participation of aluminum atoms as network formers and the intercalation of [BiO 6] and [AlO 4] entities in the [BO 4] chain network. When high Gd 2O 3 content is introduced, more [BO 3] structural units are coupled with gadolinium ions and the accumulation of oxygen can be supported by the formation of new [BO 3] −3 structural units as ortho-borate units. These yield the formation of GdBO 3 crystalline phase which has been confirmed by XRD investigations. Comparing the theoretical and experimental IR spectral characteristic features, we conclude that the prediction of the structural data is good.