New silver gallium thiophosphate glasses in the Ag<SUB>2</SUB>S-Ga<SUB>2</SUB>S<SUB>3</SUB>-'P<SUB>4</SUB>S<SUB>8</SUB>' system were studied employing a.c. impedance, Raman and IR spectroscopy. 'P<SUB>4</SUB>S<SUB>8</SUB>' does not exist and is used so that the compositions can be conventionally expressed in terms of network modifier and network formers. The glasses were in fact prepared from the elements. The trends in conductivity of other series of glasses were also studied including glasses with added AgI and mixed Ag-Na glasses. These glasses are interesting in that the phosphorus is formally in a IV+ oxidation state whereas other thiophosphate glasses previously reported in the literature contain phosphorus in a V+ oxidation state. Also, Raman spectroscopy has shown that these glasses contain hypothiodiphosphate units (P<SUB>2</SUB>S<SUB>6<SUP>4-</SUB></SUP>) which could be described as octahedral (the P-P occupies the place of the central atom). The phosphate and thiophosphate glasses studied thus far, have had structures based on meta(thio)phosphate chains of corner-sharing tetrahedra. Therefore these hypothiodiphosphate glasses are different in several respects to other thiophosphate glasses. Raman and IR studies of the 0.33Ag<SUB>2</SUB>S-0.33Ga<SUB>2</SUB>S<SUB>3</SUB>-0.33'P<SUB>4</SUB>S<SUB>8</SUB>' glass (or AgGaP<SUB>2</SUB>S<SUB>6</SUB> as it is more usually referred to in this thesis) suggest that the glass is composed of linear chains of -(Ga<SUB>1/2</SUB>P<SUB>2</SUB>S<SUB>6</SUB>Ga<SUB>1/2</SUB>)- units as proposed by Wibbelmann. Studies on the Ag<SUB>(1+x)</SUB>Ga<SUB>(1-x/3)</SUB>P<SUB>2</SUB>S<SUB>6</SUB> series lend weight to this model of the structure. The partial depolymerisation as Ga was replaced by Ag along the series could be followed by Raman spectroscopy. It was possible to relate the increase in conductivity (decrease in activation energy) along the series of changes in local structure. It was found that the compositional trends in activation energy can be explained in terms of the modified Anderson-Stuart model of Martin and Angell and in particular in terms of changes in the jump distance.

Glasses in the system v₂o₅-Te0₂ were prepared at intervals throughout the glass-forming composition range. The vanadium valence state was varied for each composition by the addition of elemental tellurium to reduce the melt. A chemical analysis method was devised to determine the v⁴⁺:vtotal ratio. Conductivity and thermopower measurements were made as functions of composition, valence ratio and temperature. The conductivity was found to increase as the total vanadium content increased and to be 21/2 to 3 orders of magnitude greater than that of a v₂0₅-P₂0₅ glass of similar v₂o₅ content. A maximum in conductivity was observed as the vanadium valence ratio was varied. This maximum was shifted to values around v⁴⁺:vtotal = 0.2 from the theoretically predicted value of 0.5. At temperatures above 250 K the conductivity varied exponentially with temperature with activation energies in the range 0.25 to 0.40 eV. Below this temperature there was a continuous decrease in slope of the conductivity down to the lowest temperature at which measurements were made. Thermopower was found to be negative and temperature independent above 250 K, while below this temperature it decreased in an activated manner with an activation energy of 0.02 eV. As a function of valence ratio the thermopower followed the behaviour predicted by Heikes and Ure, with the exception that the change of sign occurred at v⁴⁺:vtot ratios of around 0.2, instead of the theoretically predicted value of 0.5. (iii) Measurements were made of the optical absorption coefficient as functions of photon energy, composition, valence ratio and temperature. Temperature and composition did not affect the absorption spectrum significantly except that an absorption band appeared below the fundamental absorption edge as the glasses were reduced. The high electric field and a.c. properties of the glasses were also measured. These are consistent with hopping conduction of carriers between v⁴⁺ and v⁵⁺ sites. This data gives indirect indications of an inhomogeneous glass structure.