Phenomenon of Eu~(3+) self-reduction induced by B_2O_3 configuration structure in sodiumborate glasses

摘要

The self-reduction of Eu~(3+) to Eu~(2+) is realized in Eu_2O_3 doped sodiumborate glasses in the air condition. With increasing in B2O3 concentration, the blue emission of Eu2+ is significantly enhanced while the 615 nm emission of Eu~(3+) is soon decreased. The calculation result indicates that the [BO_4] tetrahedron are gradually replaced by BO_3 triangle with increasing in the network former B_2O_3 in the glass matrix. According to the infrared and Raman spectra analysis, the high polymeric network structure is depolymerized mainly from the complicated framework by [BO_4] linking with [BO_3] to the smaller planar BO_3-triangles consisted structure units. Accordingly, the characteristic vibrations of the relevant peaks are reflected by the orthoborate groups, boroxol rings, and pyroborate structure units, etc., decomposed in the sodiumborate glasses. In addition, the effect of the structure variation on the mechanism of Eu~(3+) reduction in borate glasses is discussed.