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Two photothermal techniques, the photothermoelectric (PTE) and the photopyroelectric (PPE) were applied to detect first-order phase transitions in some liquid thermoelectric (LTE) material. Due to its large Seebeck coefficient (about 4–5 mV K−1), a LTE based on dodecanol mixed with 10−1 mol L−1 tetrabutylammonium nitrate was selected for investigations. If the PPE method was already largely used to detect phase transitions in various materials belonging to condensed matter, the Seebeck effect, produced by a LTE, is used for the first time as a tool for the detection of phase transitions in the very same material. It was demonstrated that both methods are suitable to detect the first-order phase transitions in LTE materials, but in the case of PTE method the electrical and thermal effects at the phase transition can not be separated, and consequently, it is not possible to derive the critical behavior of the thermal parameters. However, the behavior of the static volume specific heat and dynamic thermal diffusivity, effusivity and conductivity of the investigated LTE could be obtained by using the PPE method in back detection configuration. [ABSTRACT FROM AUTHOR]

The front photopyroelectric configuration was applied to measure the thermal effusivity of some composite materials, inserted as backing layers in the detection cell. The technique is based on the scanning procedure of the coupling fluid's thickness (TWRC method). Two particular composite materials were selected for investigation: (i) a liquid one: water based nanofluids with gold nanoparticles and (ii) a solid one: urea-fumaric acid (1:1) cocrystal. The thermal effusivity was found independent on the size and concentration of gold particles. Concerning the urea-fumaric acid cocrystal, the thermal effusivity value of the compound is different from the pure starting materials, indicating the formation of the compound. [ABSTRACT FROM AUTHOR]