DIELECTRIC AND PYROELECTRIC RESPONSE IN NB SEMICONDUCTING Y-BA-CU-O/NB STRUCTURES/

A study on the dielectric and pyroelectric properties of nonmetallic, polycrystalline Y-BaCu-O thin films was performed for a range of tempe ratures (170-360K) and frequencies (2Hz-1kHz). The complex permittivit y, as a function of frequency, relaxed according to a first-order Deby e Model. This relaxation was shown to be thermally activated, with an activation energy equal to the activation energy for the de conduction of the material. The behavior of the data indicates that the polariza tion source is localized carriers near the Fermi level. Pyroelectricit y was measured over a temperature range of 170 - 290 K, showing a cons tant response over these temperatures. Moreover, the pyroelectric prop erties of YBCO exhibited a strong sensitivity to poling at elevated te mperatures, with a dramatic increase in,the magnitude of the response. The pyroelectric coefficient changed from p approximate to 400 nC/(cm (2)-K) for the unpoled case to p approximate to 20 mu C/(cm(2)-K) afte r poling with 5000 V/cm for one hour at 320 K.