Indian Journal of Pure & Applied Physics Vol. 46, October 2008, pp.719-721 Thermal and electrical properties of MoO 3 -Bi 2 O 3 -B 2 O 3 glasses Sanjay N Kishore, A Agarwal, V P Seth & M S Sheoran Department of Applied Physics, Guru Jambheshwar University of Science and Technology, Hisar 125 001 E-Mail:- sanjay2000angira@yahoo.co.in Received 28 October 2007; revised 15 May 2008; accepted 1 August 2008 Semiconducting oxide glasses of compositions xMoO 3 .(40-x)Bi 2 O 3 .60B 2 O 3 have been prepared by the standard melt- quenching technique over the range 0  x  10 (x is in mol%). The various properties such as glass transition temperature, density, molar volume and dc conductivity have been measured. The values of characteristic glass transition temperature (T g ) have been found from differential scanning calorimetry (DSC) traces and corresponding specific heat capacity (C p ) was also estimated. It is found that the density of these glasses decreases as MoO 3 content is increased due to lower degree of cross-bonding between molybdenum and non-bridging oxygen ions resulting in a weakening of glass network. The dc conductivity of these samples was measured in the temperature range 523-623K. In this temperature range, the dc conductivity increases from 10 -9 to 10 -8 S/m with increasing MoO 3 content. The values of the theoretical optical basicity of these glasses have also been determined. Keywords: Glasses, Glass transition temperature, Transition metal ions, dc conductivity 1 Introduction For the semiconducting behaviour of oxide glasses, it is necessary that the transition metal ions present should be capable of existing in more than one valence states so that conduction can take place by the transfer of electrons from lower to higher valence states. Some of the transition metals that fulfill this condition 1 are Ti, V, Cr, Fe, Co, Ni, Mo and W. The transition metal ions can be used to probe the glass structure because their outer d-orbital functions have rather broad radial distributions and their responses to surrounding cations are very sensitive 2 . It has been shown that the addition of Bi 2 O 3 leads to an improvement in the chemical durability and thermal stability of oxide glasses 3 and therefore, these glasses have technological applications such as glass ceramics, mechanical sensors, reflecting windows, etc 4,5 . Further, considering that B 2 O 3 is a good glass network former because of its higher bond strengths, lower cation size and smaller heat of fusion and therefore Bi 2 O 3 -containing glasses could be formed without other conventional network formers by rapid quenching 6 . The conductivity, in general, is controlled with the hopping of small polarons or electrons between localized states and strong electron-phonon interaction is considered to be responsible for the formation of small polarons in these glasses 6,7 . In the present work, bismuth borate glasses doped with MoO 3 have been prepared in order to study the effect of MoO 3 on the characteristics glass transition temperature (T g ), density (d) and dc electrical conductivity. 2 Experimental Details xMoO 3 .(40-x)Bi 2 O 3 .60B 2 O 3 (0  x  10) glasses have been prepared from AR grade chemicals MoO 3 , Bi 2 O 3 and H 3 BO 3. The chemicals were thoroughly mixed in appropriate proportions to yield about 15 g of the desired compositions. Then, the mixture was melted in porcelain crucibles by putting it in an electrical muffle furnace at about 1473K in air for about 30 min. The melt was swirled frequently to assure homogeneity. The melt was then quickly poured onto a stainless steel plate and pressed with another stainless steel plate to get the coin shaped samples of 1-2 mm thickness. Differential Scanning Calorimetry (DSC) of the samples was performed using a TA DSC-Q10 model with heating rate 10 0 C/min. The density of these glasses was calculated at room temperature using Archimedes’ methods with xylene as the immersion liquid. The molar volume was also calculated using the relation V m = M/d, where d is the density and M is the molecular weight of each sample. A part of each sample was annealed at 473K for 2h. To measure the dc conductivity, annealed samples in the form of slices of nearly 1mm uniform