Pyroelectric effects in thin film

The pyroelectric effect in a thin film rigidly attached to a thick substrate is discussed and compared to the usual (stress-free) effect. The effects of clamping are negligible for the geometry normally used in pyroelectric detectors in the case of three proper ferroelectric-type pyroelectric materials of practical interest, namely, LiTaO₃, Pb₅Ge₃O₁₁, and Sr_0.5Ba_0.5Nb₂O₆. In the case of three wurzite-type (nonferroelectric) pyroelectrics, namely, CdS, CdSe, and ZnO, the pyroelectric effect is drastically reduced by such clamping. Thus the pyroelectric effect in the latter materials appears to be piezoelectric in origin, in contrast to the case of most pyroelectric materials.