Seiji Inaba

Heat capacity of oxide glasses at high temperature region

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. Our previous study has revealed that heat capacities of oxide glasses scaled with the molar heat capacity at the Debye temperature have a similar magnitude and temperature dependence from 300 K to glass transition temperatures. On the basis of this observation, the factor effecting heat capacity was investigated by use of the three-band theory which is composed of separate contributions from one- and three-dimensional Debye model and Einstein model. We revealed that the heat capacity of oxide glass in the temperature range of measurements follows the one-dimensional Debye model and the compositional variations of heat capacity are evaluated in terms of the ionic packing ratio and the dissociation energy of oxide glass.

Heat capacity of oxide glasses measured by AC calorimetry

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.