Technique for the measurement of thermal diffusivity based on the laser intensity modulation method (LIMM)

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Abstract
A new technique has been developed for measurement of the thermal diffusivity of samples with thicknesses in the range from several micrometers to about a millimeter. The test sample is attached to a thin sheet of electroded and poled polyvinylidene fluoride (PVDF) which acts as a pyroelectric detector. The other surface of the sample is illuminated with a sinusoidally-modulated laser beam which causes the propagation of temperature waves through the sample into the PVDF. The phase retardation of the waves, which is a unique function of the sample thickness and thermal diffusivity, is determined from the pyroelectric current generated by the PVDF. The thermal diffusivity of the sample is then found by matching the experimental phase angle measurements to the analytical solution using a minimization algorithm. Computer simulation calculations are used to make an error analysis. Experimental results for five polymeric and two ceramic materials are presented.