The specific heat capacities of V2O5/P2O5-based glasses

The specific heat capacities of a series of V₂O₅/P₂O₅-based glasses have been measured in the approximate temperature range 3–300 K. The proportions of the host constituents were varied and the effects produced by adding oxides of copper, titanium and sodium were examined. The measurements were extended to investigate the influence of fast neutron irradiation upon the specific heat capacity of pure, initially crystalline V₂O₅.The observations are consistent with a spectrum of background vibrations, the form of which is temperature dependent. At intermediate temperatures the vibrations were consistent with the glasses displaying predominantly chain-like characteristics. With reduction to lower temperatures the vibrational behaviour increasingly resembled that of solids displaying three-dimensional characteristics. The temperature dependence of the specific heat capacity at the lowest temperatures was consistent with the presence of a narrow band of low-frequency modes centred upon 1.67 × 10¹¹ s^?1, the density of which increased with phosphorus content. From observations of the density of these modes in the doped specimens, it was concluded that the role of copper wass largely that of a network former, whereas titanium and sodium were essentially network modifiers.