Lock-in thermography versus PPE calorimetry for accurate measurements of thermophysical properties of solid samples: a comparative study

The aim of this paper is to compare the measurement accuracy of photopyroelectric calorimetry in back detection configuration (BPPE) and infrared lock-in thermography (LT) for thermal diffusivity measurement of solid samples. For this purpose, the following materials with well-known thermal properties have been selected: glassy carbon (type G), LiTaO3 crystal and binary II-VI semiconductors (based on CdSe and CdTe). The advantages and drawbacks of the two techniques have been analyzed both theoretically and experimentally

Thermal characterization of II–VI binary crystals by photopyroelectric calorimetry and infrared lock-in thermography

In this paper, a complete thermal characterization (measurement of all static and dynamic thermal parameters) of some selected II-VI binary crystals was carried out. The semiconductors under investigation were grown from the melt by high-pressure/high-temperature modified Bridgman method. The contact photopyroelectric (PPE) method in back configuration (BPPE) and non-contact infrared lock-in thermography technique were used in order to get the thermal diffusivity of the investigated crystals. The thermal effusivity of the samples was obtained by using the PPE technique in the front configuration (FPPE), together with the thermal wave resonator cavity (TWRC) method. Knowing the values of the thermal effusivity and thermal diffusivity, the remaining two thermal parameters, i.e., thermal conductivity and specific heat were calculated

On the optimization of experimental parameters in photopyroelectric investigation of thermal diffusivity of solids

In this paper, the possibility of optimizing the experimental conditions for a correct photopyroelectric evaluation of the thermal diffusivity of solid samples is studied. For this purpose, a glassy carbon sample, with known thermal properties, was selected as test material and two types of techniques were applied in order to get the value of its thermal diffusivity: (i) the photopyroelectric calorimetry in back detection configuration and (ii) the infrared thermography. Assuming that the values of thermal diffusivity obtained by thermography are correct (a non-contact technique), we studied how to eliminate the underestimation (due to the presence of the coupling fluid) of the results in the back photopyroelectric calorimetry investigations. Experiments with different types of coupling fluids and numerical simulations were performed in order to evaluate the influence of the coupling fluid on the value of the thermal diffusivity. The conclusion is that a proper choice of the type of coupling fluid and some improvements performed in the experimental design of the photopyroelectric calorimetry detection cell (with the purpose of reducing the coupling fluid’s thickness), can eliminate the difference between the results obtained with the two photothermal (contact and non-contact) techniques

Thermal characterization of ZnBeMnSe mixed compounds by means of photopyroelectric and lock-in thermography methods

In this work a thermal characterization (measurement of dynamic thermal parameters) of quaternary Zn1-x-yBexMnySe mixed crystals was carried out. The crystals under investigation were grown from the melt by the modified high pressure Bridgman method with different Be and Mn content. The effect of Be and Mn content on thermal properties of Zn1-x-yBexMnySe compounds was analyzed, by using the photopyroelectric (PPE) method in the back configuration (BPPE) for thermal diffusivity measurements, and the PPE technique in the front configuration (FPPE) for thermal effusivity investigations. Infrared lock-in thermography (IRT) was used in order to validate the BPPE results. The measured thermal effusivity and diffusivity allowed the calculation of thermal conductivity of the investigated materials

Quantitative thermal wave phase imaging of an IR semi-transparent GaAs wafer using IR lock-in thermography

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