Structural and dc electrical conductivity studies of SnO substituted lead vanadate glasses

Glasses of the system x (SnO) (50-x)PbO : 50V2O5 were prepared by melt quenching in the range x = 0 mole% to 15 mole%. Measurements are reported for dc electrical conductivity for the above compositions in the temperature range 300K-500K. The experimental results are analyzed with reference to various theoretical models proposed for dc electrical conduction in amorphous semiconductors. The analysis shows that at high temperatures the temperature dependence of dc conductivity is consistent with Mott's model of phonon-assisted hopping conduction, variable range hopping mechanism and Schnakenberg's model mechanism. The hopping in this system is of an adiabatic in nature. 1. INTRODUCTION In view of their potential applications, research on amorphous semiconductors in thin film or bulk form has been receiving increased attention. Semi-conducting oxide glasses like lead vanadate have also been studied to a considerable extent. In addition to their potential application, basic understanding of the physical properties of these materials is itself of great fundamental importance. Considering the enormous variation in the composition of these glasses the scope for research is also very wide. Of late in this laboratory lead metavanadate has been identified as a suitable glass system whose physical properties show considerable variations due to the influence of the substitution of different metal oxides in the place of lead oxide. In the conventional silicate based glasses electrical conduction takes place due to ionic transport. In semi-conducting glasses the electrical conduction is due to the transport of electrons. The research in understanding the structural and physical properties of glasses in general and semi-conducting glasses in particular has increased considerably due to the potential applications perceived for semi-conducting glasses These glasses are known to contain V 4+ and V 5+ ions and conduction is attributed to hopping of a 3d 1 electron from V 4+ to V 5+ site (N. Among vanadate glasses PbO: V2O5 has received greater attention because of its wider glass-forming region in the phase diagram (J.M. Marshal et al., 1971). The PbO: V2O5 in 1: 1 molar ratio is at the eutectic composition giving a stable metavanadate (PbV2O6) crystalline phase with known crystal structure (R.A. Street et al., 1975). The lead metavanadate phase in glass as well as in crystalline forms were subjected to several studies using Electron Spin Resonance (ESR) (N.F. Mott et al., 1975), magnetic susceptibility (N.F. Mott et al., 1979) , thermodynamic measurements, electrical properties. The present paper contributes the results …