Overcoming the influence of the coupling fluid in photopyroelectric measurements of solid samples.

The thermal diffusivity of solid samples is systematically underestimated in a photopyroelectric technique used in the standard back configuration due to the presence of the coupling fluid between sample and detector. In this work, we propose a new method to overcome the undesired effect of the coupling fluid. It relies on the use of a transparent pyroelectric sensor and a transparent coupling fluid, together with a self-normalization procedure. In this way, we are able to measure accurately (a) the thermal diffusivity of opaque solid samples, and (b) the thermal diffusivity and the optical absorption coefficient of semitransparent solid samples.