Optical absorption and photoluminescence properties of anadium ions in 'lithium-tungsten-borate' oxide glasses. (2018)

• Record Type: Journal Article
• Authors: Srinivasa Rao, L.; Ravi Kumar, V.; Naresh, P.; Venkateswara Rao, P.; Veeraiah, N.
• Is Part Of: Materials today. Volume 5:Number 13(2018)Part 1
• Page Start: 26290
• Page End: 26297
• Publication Date: 2018
• Subjects: Oxide glasses -- Vanadium ions -- Optical absorption -- Photo luminescence; Materials science -- Congresses -- Periodicals; 620.1
• DOI: 10.1016/j.matpr.2018.08.079
• Languages: English
• ISSNs: 2214-7853

Abstract

Abstract: 40Li2 O–5WO3 –(55–x) B2 O3 : xV2 O5 glasses for x = 0.0, 0.2, 0.4, 0.6 and 0.8 (all in mol %) were prepared by melt-quenching method. The glasses were characterized by X-ray diffraction spectra, optical absorption spectra and photoluminescence spectra. The XRD patterns confirmed the amorphous nature of the glass samples. The optical absorption spectra of the glasses have exhibited two broad absorption bands of VO 2+ ions with meta-centers around 630 nm and 990 nm corresponding to 2 B2g → 2 B1g and 2 B2g → 2 Eg transitions respectively. From the observed absorption edges, we have evaluated the optical band gap (E o ) of the glasses by drawing Tauc's plots. The photoluminescence spectra (excited at 639 nm) of the glasses have exhibited a broad emission band with meta-center at around 800 nm. The interpretation of results shows that as the content of V2 O5 increases up to 0.6 mol % in the glass system, the optical band gap (E o ) decreases and the intensity of the emission peak increases with red shift due to gradual conversion of vanadium ions from V 5+ state to V 4+ state. Thus, these investigations point out that the vanadium ions coexist in V 4+ state with V 5+ state. More precisely, when x ≤ 0.6 mol %, the V 4+ ions are expected to be dominant in the glass system which act as network modifiers; whereas when x = 0.8 mol %, the V 5+ ions seem to prevail, acting as network formers with VO5 structural units in the glass matrix.