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In this paper we combine the use of photo-thermal techniques, Thermal lens (TL) spectrometry, Photoacoustic and heat capacity measurements to determine the optical path dependence with temperature (ds/dT) of a polycrystalline 3C-SiC sample. Results obtained for the polycrystalline sample with the TL technique show that ds/dT is negative at room temperature. This means that the thermal lens formed in 3C-SiC acts as a divergent lens when light impinges the sample. Our measurements, demonstrate that photo-thermal techniques can be used to obtain thermal parameters in circumstances where other techniques cannot be used, for example, in harsh environments.

In this paper, we describe a new, simple, and fast photothermal method for simultaneous measurements of two important gas thermal properties: thermal diffusivity and thermal effusivity. The method consists essentially in combining a photoacoustic cell and a thermal wave pyroelectric cell enclosed in a single compact gas analyzer. The photoacoustic cell is kept filled with synthetic air and sealed. The pyroelectric cell is also filled with synthetic air, and after some warm up time, the synthetic air is exchanged to the gas of interest. It is shown that the analysis of the transient and saturation signals of both photoacoustic and pyroelectric cells is capable of measuring the thermal properties with an accuracy of 3%. This particular capability of performing simultaneously the measurements of thermal diffusivity and thermal effusivity allows us to carry on the complete characterization of the thermal properties of gases.