HIGH DIELECTRIC-CONSTANT AND NONLINEAR ELECTRIC-RESPONSE IN BI2SR2SMCU2OY

Samples with the nominal composition Bi2Sr2SmCu2Oy were prepared by so lid state reaction method. From the room temperature X-ray diffraction data, it was found that the sample is similar to the Bi-2212 structur e. DC electrical resistivity was done from 80 K to 573 K and the imped ance measurements were performed from 80 K to 573 K at different frequ encies in the range of 10 kHz to 800 kHz. The sample Bi2Sr2SmCu2Oy has exhibited semiconducting behavior in the low temperature region (80 K to 343 K), metallic behavior in the temperature range of 343 K to 443 K and again semiconducting behavior above 443 K. The sample has exhib ited the phenomenon of variable range-hopping mechanism (VRH). The phy sical parameters related to VRH such as localization length (a), hoppi ng distance (R) and hopping energy (W) have been evaluated and discuss ed. The activation energy in the high temperature region (above 300 K) decreases with increasing frequency. Tan delta increases with increas e in temperature (303 K-573 K), which is attributed to increased condu ctivity. The dielectric constant increases with increase in temperatur e. For a given temperature the value of epsilon is found to decrease w ith increase in frequency.