Self-normalized photoacoustic technique for thermal diffusivity measurements of transparent materials

A self-normalized photoacoustic methodology for thermal diffusivity measurements of thin foils of transparent materials is presented. The methodology implementation involves attaching a high optically opaque thin film on one of the transparent sample's surface. The corresponding measurement procedure involves the analysis of the normalized phase, as a function of the modulation frequency, in the thermally thin and thick regimes. Since the purely thermal-diffusion-wave mechanism is assumed then simple experimental criteria, to ascertain that this is the case in the selected modulation frequency range, is also reported. Three different materials were examined using the proposed methodology: cover glass slabs and thin foils of acetate and polyvinylidene difluoride polymers.