Potential distribution in a bounded piezoelectric in the presence of the photothermoacoustic effect

The photothermoacoustic effect in a bounded piezoelectric is studied theoretically and experimentally. Calculations are made of the potential distribution over the thickness and the potential difference in a thin piezoelectric layer as a function of the coordinate of this layer. The amplitude distribution of the potential oscillations over the thickness of the piezoelectric reveals two maxima. The phase of the oscillations at these maxima is shifted by approximately 180°. It is shown that the potential difference on the opposite surfaces of the plate is zero regardless of the propagation constant of the thermal wave. An experiment was carried out using a layered disk formed by seven identical piezoelements. The amplitude and phase shift of the potential difference were investigated for each element at different light modulation frequencies. The experimental results show good agreement with the theory.