Heat capacity of oxide glasses measured by AC calorimetry

Abstract

Heat capacities of vitreous silica, and some binary and ternary silicate, borate, and phosphate glasses were measured in the temperature range from 300 to 840 K by AC calorimetry. In this method, the conditions of measurement, especially AC frequency and sample thickness, must be examined in order to measure the heat capacity with high accuracy, and thus, an optimum condition for measuring the heat capacity was investigated. The relationship between heat capacity and chemical composition was discussed in terms of the Debye model, which can be used for calculation of the heat capacity of atomic solids. We found that heat capacities of all the samples studied here scaled with the molar heat capacity at the Debye temperature have a similar magnitude and temperature dependence, from 300 K to the glass transition points. Based on this observation, we propose an empirical equation which is composed of separate contributions of the compositional and temperature dependence of the heat capacity.