Abstract
Among the photothermal methods, the photopyroelectric (PPE) technique is a suitable method to determine thermal properties of different kinds of samples ranging from solids to liquids and gases. Polyvinylidene difluoride (PVDF) is one of the most frequently used pyroelectric sensors in PPE technique but has the disadvantage that it can be easily deformed by the sample weight. This deformation could add a piezoelectric effect to the thermal parameters assessment; also PVDF has a narrow temperature operation range when compared with ceramic pyroelectric sensors. In order to minimize possible piezoelectric effects due to sensor deformation, a ceramic of lanthanum modified lead zirconate (PLZT) was used as pyroelectric sensor in the PPE technique. Then, thermal diffusivity of some liquid samples was measured, by using the PPE configuration that denominated the thermal wave resonator cavity (TWRC), with a PLZT ceramic as pyroelectric detector. The performance obtained with the proposed ceramic in the TWRC configuration was compared with that obtained with PVDF by using the same configuration.
Highlights
In recent years, the photothermal (PT) methods have developed useful experimental configurations in order to evaluate the thermal and optical properties of materials [1]
PLZT hardness prevents the deformations that in thin Polyvinylidene difluoride (PVDF) sheets occur due to the sample weight; these deformations could add a piezoelectric effect in the measurement
A PLZT was used as PE detector in order to obtain the thermal diffusivities of different liquid samples as distilled water, olive oil, glycerol, and ethylene glycol by the thermal wave resonator cavity (TWRC) method
Summary
The photothermal (PT) methods have developed useful experimental configurations in order to evaluate the thermal and optical properties of materials [1]. PT methods can provide direct optical absorption spectra, the characterization of thermal properties, and analysis of nonradiative relaxation processes. These methods have been used to determine thermal parameters of solid, liquid, and gaseous samples [1]. Among the PT methods used to examine thermal properties of liquids stands the thermal lens (TL) spectrometry This PT technique has been used to study nearly transparent liquids, with the disadvantage that light is scattered when solid particles are suspended into the liquid [2]; in order to avoid light scattering, an indirect sample heating can be used by using another PT method as the PPE technique. In the present study is described the thermal wave resonator cavity (TWRC) method, based on a PPE detection, using a pyroelectric ceramic as a sensor in order to improve the pyroelectric detection of thermal waves
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