AN APPROACH FOR STUDYING NATURAL UNIPOLARITY IN DOPED AND PURE SINGLETGS-CRYSTALS

An investigation was made to study the dependence of the magnitude and direction of the pyroelectric current on the internal biasing field a nd natural unipolarity for both pure and doped TGS single crystals, Th e effect of applying poling electric fields, both parallel and antipar allel to the direction of the natural unipolarity, on the behavior of pyroelectric current was also inspected. A negative pyroelectric curre nt was observed during the second subsequent heating runs for pure TGS crystal and for one, with Co+2 doping. For one pure sample, pyroelect ric current followed the direction of the direction of the applied pol ing field, white for another pure one taken from a neighboring site, t his was not the case. Stronger electric fields were needed to overcome the internal biasing field, in order that the pyrocurrent may be able to follow up the direction of the poling field. On the other hand, fo r a crystal doped with Co+2 ions, even a poling field of up to 4KV/cm was not enough to overcome the internal field; the sample retained its behavior. All the observed irregularities were attributed to the infl uence of the internal field together with the crystal inhomogeneity.