An Optical-Based AC Calorimetry Method to Simultaneously Measure the Thermal Conductivity and Heat Capacity of Poor Thermal Conductors

Conventional AC calorimetry method uses a modulated laser to periodically heat up a suspended thin-film sample and a thermocouple to measure the thermal wave signals at different locations from the heating spot. The in-plane thermal diffusivity of the sample can be extracted from the amplitude attenuation (amplitude approach) or the phase lag (phase approach) as a function of distance between the heating and detecting spots. This paper proposes a novel optical-based AC calorimetry method to simultaneously measure the thermal conductivity and heat capacity of lowly conductive materials. This method is demonstrated and validated through the measurements of an amorphous silica sample. This paper also conducts uncertainty analysis and discusses the selection of the optimal spot size and modulation frequency used for the measurement. © 2024 Science Press. All rights reserved.