[Study of thermal diffusivity by piezoelectric photoacoustic phase]

Piezoelectric photoacoustic phase information can be applied to determine the thermal diffusivity of sample. In actual experiments, the results of phase versus modulation frequency deviate from the theory heavily because of the disturbance of instrumental contribution from the whole detecting system. Considering that the instrumental contribution of phase from PA cell can be ignored reasonably, there will be no additional phase contribution after the piezoelectric PA cell has been replaced by microphone PA cell while the other experimental conditions have been kept invariable. Based on this hypothesis, the conventional photoacoustic cell with microphone is employed to determine the instrumental contribution of whole detecting system by studying the PA phase of solid rare earth complexes. The instrumental contribution of phase was considered to be constant for that the same detecting system was used in both the microphone PA method and piezoelectric PA method. This method has been proved by detecting the thermal diffusivity of aluminium sample. The corrected results of experiments match the theory well, showing that the method of subtracting the instrumental contribution from the original experimental phase can be applied reasonably in relevant chopping frequency region. While in lower chopping frequency region, there will be a little deviation from the theoretical results. The method has been also employed to the photoacoustic detection of leaf, and the thermal diffusivity of leaf can be acquired by studying the piezoelectric photoacoustic phase.