An extension to the methodology for characterization of thermal properties of thin solid samples by photoacoustic techniques

• Intersection frequency (IFr) is the frequency where the magnitudes of the TE and TD components of PA response are equal.
• Analytic expressions for the IFr may be derived If it belongs to the low-frequency or to the high-frequency range.
• Experimental detection of the IFr enables derivation of one relation between thermal parameters of thin samples.
• The obtained expressions for thermal parameters of thin samples have high calculation errors, and should be used carefully.

The paper presents a study of possibilities to extend the present methodology for thermal characterization of thin solid samples by photoacoustic techniques. The present methodology consists of linear fitting of the experimental data to approximate the expressions derived from the composite piston model of photoacoustic response and it is mainly used for calculation of thermal diffusivity of thin samples. The study has shown that the methodology may be extended to calculation of thermal diffusivity, thermal conductivity and thermal expansion coefficients of thin samples by linear fitting in multiple frequency ranges and by analysis of the intersection frequency, which is the frequency where the magnitudes of two components of photoacoustic response in the composite piston model are equal. The analysis of numeric errors of the methodology has revealed the dominant sources and magnitude of the errors, leading to the conclusion that photoacoustic techniques should be carefully used as a tool for extensive thermal characterization of thin samples in the cases when other techniques are not applicable or have larger errors.