Improved method for simultaneous determination of thermal properties

An improved method to simultaneously determine the heat capacity, thermal diffusivity, and thermal conductivity of a small-sized material is described. In this method, the heat of a square wave with a superimposed constant component is applied to one side of a plate-shaped sample using a thin-film heater, which is thermally linked to a heat reservoir. The response temperature is measured by a thermometer attached to the heater. In contrast to a previously reported method, the amplitude of the temperature oscillation detected by the thermometer is enhanced by the internal thermal relaxation in the improved method. This feature is advantageous for determining thermal properties with low-heat modulation. We theoretically analyzed the proposed method using a one-dimensional model and demonstrated the method on synthetic quartz (SiO2) and poly(methyl methacrylate) plates in the temperature range of 80-300 K. The thermal properties obtained for both samples using the proposed method were consistent with values reported in the literature. The deviations from the data for the specific heat capacity, thermal diffusivity, and thermal conductivity were estimated to be ∼1%, 2%, and 2%, respectively.