An investigation for new type of varistor based on BSCCO ceramics

Yttrium-substituted Bi(Pb):2212 and Bi(Pb):4212 ceramic samples are prepared by using the well-known solid-state reaction method. The considered samples are investigated for phase purity and grain morphology by using X-ray diffraction (XRD) and scanning electron microscope (SEM). While current–voltage (I–V) characteristics are obtained from dc electrical measurements in two different situations, the first is taken by using silver paint for the electrical contacts of the samples; the other is taken without using any silver paint for the contacts. It is found that I–V characteristics are ohmic behavior in the low-field region for the two considered samples in the two cases. With increasing field, the nonlinear behavior is clearly observed in the latter case and is still absent in the former case. Furthermore, the nonlinear coefficient, breakdown field and barrier voltage are also obtained for the two samples and it is found that their values are higher in Bi(Pb):4212 sample than in Bi(Pb):2212 sample. These results increase the possibility to investigate these two samples as a new type of varistor as well as in ZnO ceramics.