Borate speciation and structural studies of vanadium ion doping in borate bioglass

Abstract

Abstract Different glasses in the system, x V 2 O 5 -(45– x )B 2 O 3 –24.5Na 2 O–24.5CaO–6P 2 O 5 , ( x = 0, 3, 6, 9, 12, 15, 18, 20 and 25 Wt%) were prepared through melt quenching method. X-ray diffraction (XRD) patterns have revealed that the amorphous structure is the dominant type. There is no tendency for crystallization even with higher vanadium content. Crystallization occurred utilizing treating the glasses thermally. FTIR spectral absorption data showed the presence of both BO 3 and BO 4 structural groups in combination with the presence of VO 4 and VO 5 structural building units. The deconvolution analysis technique (DAT) was adopted to retrace the conversion progressions of the coordinated boron. At low V 2 O 5 content (up to 10 wt%), it entered as a glass modifier as well as both Na 2 O and CaO. The high content of the glass modifier (Na 2 O + CaO + V 2 O 5 ) could destroy some of the well-formed BO 4 units which are transformed into asymmetric BO 3 . The back conversion of BO 4 to asymmetric or loose BO 3 can simply reduce the fraction of tetrahedral units ( N 4 ). When V 2 O 5 entered as a glass former (> 10 wt%), the N 4 fraction increased. The change in the measured densities and estimated molar volumes may assigned to the formation of BO 4 units resulting from increasing vanadium oxide content.