DEPENDENCE OF THE DIELECTRIC RESPONSE OF PB(SC0.5TA0.5)O3 ON APPLIED DC FIELD - IMPLICATIONS FOR THE CHOICE OF TARGET MATERIALS IN THERMAL IMAGING DEVICES

It has recently been suggested1 that by operating a ferroelectric pyroelectric under a d.c. field its dielectric response can be modified to improve its sensitivity as a pyroelectric imager target. In light of this, a knowledge of how the various classes of pyroelectrics respond to field would be useful. Lead scandium tantalate (PST) materials were chosen as the subject of the present study. Samples were synthesized by a conventional ceramic route, and subjected to extensive measurements in order to determine the response of their relative permittivity, loss tangent, and pyroelectric coefficient to applied d.c. fields. Using these data the predicted performance of a thermal imager operated with a PST target has been calculated: the highest performance was obtained with the most ordered material, which gave a thermal resolution (noise equivalent temperature difference) of 0.11 K.