Measurement of phase transitions and thermal diffusivity in agar using a thermal wave resonator cavity

Abstract
In the present work, the photopyroelectric (PPE) technique is proposed using a Thermal Wave Resonator Cavity (TWRC) to measure the temperature dependence of the thermal diffusivity of agar. Also, to determine the liquid to gel phase transition temperature on several agar concentration samples. The thermal diffusivity of agar as a function of temperature was measure by means of a cavity length variation due to thermal expansion of the TWRC, instead of the typical mechanic length variation through a micrometer. A change in the liquid to gel transition phase temperature was detected as a function of agar concentration, getting lower values as the agar concentration decrease.