Studies of the electronic properties of some transition metal ion glasses
Three series of glasses were prepared and studied. They include the barium-vanadate, the barium-tellurite series and a series of tellurium-vanadate glasses, the first two series being modified by the inclusion of barium chloride and the third by the adition of barium oxide. It was found for each series that glasses could be obtaind within well-defined limits of composition. Properties studied included a detailed investigation using electron paramagnetic resonance(electron spin resonance) which enables reduced valency states to be evaluated and measurements of density, electrical conductivity and optical absorption measurements in the vicinity of the absorption edge and in the infra-red region were made. X-ray diffraction was used to establish the non-crystalline character of the samples. Standard wet chemical analysis and atomic absorption analysis were used to determine the total vanadium ion content for comparison with values inferred from the e.s.r. measurements . All samples were studied after the glass forming and initial annealing process but a number of samples were given longer periods of annealing. The semiconducting properties of the glass systems without halogen or BaO addition were typical of many similar glass systems. The e.s.r. results gave useful estimates of the normal and reduced valency constituents and these compared reasonably with the results of chemical analysis. The replacement of oxygen by chlorine gave results, which although comparable with earlier reports on copper- phosphate glasses containing chlorine, nevertheless presented problem of interpretation. As the BaCI2 content was increased, the electrical conductivity and concentration of the paramagnetic ions decreased steadly up to about 7mole% but with further addition of BaCI2, the DC conductivity and spin concentration increased again. The possible reasons for this observation were discussed and involved a change in the behaviour of chlorine ion bonding or possibly a clustering of chlorine ions for samples with higher chlorine content. The results are discussed in terms of recent ideas on the science of amorphous meterials.