Accurate photopyroelectric measurements of thermal diffusivity of (semi)liquids

The back photopyroelectric (PPE) configuration, with opaque sample and thermally thick sample and sensor, was applied in order to obtain room temperature values of the thermal diffusivity of some (semi)liquid materials. The methodology is based on a sample's thickness scan, and not on a frequency scan as usually happens. The possibility of controlling, very accurately, the sample's thickness variation, leads to very accurate and reproducible values for the thermal diffusivity. A special detection cell was designed in order to control the sample's thickness within 1 ýýýým precision. Due to the high accuracy of the results one can study, via the thermal diffusivity, processes as sedimentation, the capture of water molecules by OH radicals in alcohol–water mixtures, or the quality of lipids (i.e., margarine