Physics and Chemistry of Glasses: European Journal of Glass Science and Technology Part B Volume 56 Number 4 August 2015 169 Phys. Chem. Glasses: Eur. J. Glass Sci. Technol. B, August 2015, 56 (4), 169–174 1. Introduction Phosphate glasses have superior physical proper- ties such as low melting temperature, high thermal expansion coefficient, strong glass forming ability, high electrical conductivity and simple structure. Because of this, phosphate glasses have aracted increased recent aention compared with silicate or borate glasses (1–4) and also these properties make them useful candidates for fast ion conducting materials. (5) During the last two decades phosphate glasses have been investigated intensively, but there is still a great interest in developing new glasses related to the demands of both industry and technology. These glasses have poor chemical durability that often limits their usefulness, but which can be improved by the substitution of various oxides such as lead oxide. (6,7) In the last decades lead oxide was not only used as a constituent in several borate glasses, (8,9) but also in phosphate glasses (10) in order to reach new and useful physical and chemical properties for technological applications. The structural role of PbO in many oxide glasses is interesting because it has been demon- strated that it plays a dual role, as network modifier and the former. (11) Several interesting properties of phosphate glasses have been found to result from the incorporation of PbO into the glass network. For instance, PbO is useful for shielding against high energy radiations, including nuclear radiation (12) and its addition may result in the formation of P–O–Pb bonds. These bonds also lead to an improvement of the chemical durability of phosphate glasses. (13) The introduction of MoO 3 in phosphate glasses leads to the formation of various molybdenum units that enter into the glass network by crosslinking phosphate chains. (14,15) Infrared spectroscopic inves- tigations of a few PbO modified molybdophosphate glasses reveals that the addition of the modifier de- polymerises the phosphorous–oxygen chain by form- ing new P–O–Pb bonds and nonbridging oxygens in the network. (16) A few studies of the compositional dependence of the glass network structure in a few molybdophosphate glasses show that increasing MoO 3 content leads to the transformation of Mo–O− and P–O bonds into Mo–O–Mo and weaker Mo–O–P bridging bonds. (17,18) Semiconducting transition metal oxide glasses have gained importance in recent years due to their possible applications in various tech- nological fields. (19–22) Transition metal ions are very interesting ions to probe in glass networks because of their broad radial distribution of outer d-orbital electron functions and their sensitive response to the surrounding cations. (23–26) Among various semi- conducting transition metal oxide glasses, vanadate glasses find applications in memory and switching devices. V 2 O 5 is known to participate in the glass network with VO 5 pyramidal structural units. Several vanadate glasses show semiconducting behaviour with electrical conductivities of 10 −3 –10 −5 (Wcm) −1 , which is known to be due to electron hopping between V 4+ to V 5+ ions in the glass network. The content of vanadium in different valence states in the Spectroscopic investigations of the PbO–MoO 3 –P 2 O 5 :V 2 O 5 glass system P. Syam Prasad, 1* V. Himamaheswara Rao, 1 M. Mohan Babu, 1 P. Venkateswara Rao, 2 G. Naga Raju 3 & C. Laxmikanth 4 1 Department of Physics, National Institute of Technology, Warangal, India 2 Department of Physics, The University of the West Indies, Mona campus, Kingston 7, Jamaica 3 Department of Physics, Krishna University-PG Centre, Nuzvid, India 4 Department of Physics, The University of Dodoma, Tanzania Manuscript received 20 January 2015 Manuscript accepted 12 February 2015 V 2 O 5 doped PbO–MoO 3 –P 2 O 5 glasses were prepared by melt-quenching and the amorphous nature of these samples was confirmed by XRD. EPR data indicate the presence of V 4+ ions in a square-pyramidal coordination (C 4v ). The experimental EPR spectra were simulated assuming a superposition of two signals; one with hyperfine structure (HFS) typical for isolated ions and the other one consist of a broad line without HFS characteristic of clustered ions. The optical absorption spectra of the glasses exhibited two broad absorption bands corresponding to 2 B 2 Æ 2 B 1 and 2 B 2 Æ 2 E transitions of VO 2+ ions, with increasing concentration of V 2 O 5 , the half width and peak height of these bands were observed to increase. The IR bands of phosphate groups were strongly reduced for 0·6 mol% of V 2 O 5 due to the depolymerisation of the phosphate network and to the appearance of new vibrations characteristic of P–O–V and V–O–V linkages showing the network former role of V 2 O 5 . *Corresponding author. Email syam9405@gmail.com Original version presented at the International Seminar on Glasses and Other Functional Materials (ISGFM), Andhra Pradesh, India, 11–13 December 2014 DOI: 10.13036/17533562.56.4.169