Normal-state dielectric and transport properties of In-doped Bi–Pb–Sr–Ca–Cu–O

Abstract

The effect of indium doping on the normal-state transport and dielectric properties of the Bi 1.84Pb 0.34Sr 1.91Ca 2.03Cu 3.06In x O y (0≤ x≤0.15) has been investigated. The dielectric constant, loss tangent, carrier concentration and electrical resistivity were measured at room temperature as a function of indium concentration. The dielectric constant is found to increase with increasing dopant concentration possibly due to increase in polarization. Impurities in any crystalline lattice generally cause deformation of the surrounding volume and modification in the local fields. The loss tangent of the indium doped-system decreased with increasing dopant concentration. Decrease in the loss tangent with increase in the dopant concentration indicates the decrease in the dielectric losses in the sample during doping. The carrier concentration is found to decrease with increasing indium concentration. This could be due to charge imbalance, which leads to a decrease in the number of holes in the system. Consequently, the electrical resistivity at 50 °C increased with the dopant concentration. Also, above x=0.05 dopant concentration there was a rapid rise in electrical resistivity, possibly due to disorder in the Cu–O 2 planes. The temperature dependence of the electrical resistivity above room temperature is consistent with metallic behavior.