On the photothermal characterization of liquid thermoelectrics. New methodology based on coupled pyroelectric-Seebeck effects, together with frequency and thickness scanning procedures

A new, combined photopyroelectric-photothermoelectric (PPE-PTE) technique, coupled with both thickness (TWRC) and chopping frequency (FS) scanning procedures, is proposed for thermal characterization of liquid thermoelectrics (LTE). The PPE-TWRC technique, in back detection configuration was used for the direct measurement of the LTE's thermal diffusivity. Based on the results obtained for thermal diffusivity, two PPE-FS scans, performed at two different thicknesses are used for the precise determination of absolute LTE's thicknesses. Simultaneously, PTE-FS scans, performed at the same thicknesses, lead to the value of LTE's thermal effusivity. The main advantage of the proposed technique, compared with previously reported procedures based on the TWRC scan, is a more precise determination of absolute LTE's thickness. In such a way the possible influence of the slow Soret effect is eliminated. The results, obtained on octanol + 0.1 mol l−1 TDAN (tetradodecylammonium nitrate), α = 6.77 × 10−8 m2s−1, e = 602 Ws½ m−2 s−1, k = 0.15 W m1 K−1, are in good agreement with previously reported data.