Dielectric properties of semiconducting Bi_4-nPb_nSr₃Ca₃Cu₄O_x (0 ≤ n ≤ 1) glasses: Precursors for high-T_c, superconductors

Abstract

The dielectric constant (ε′) and loss (ε″) for Pb-doped Bi_4-nPb_nSr₃Ca₃Cu₄O _x, (n = 0.0, 0.1, 0.5 and 1.0) glasses, which become high-T _c superconducting oxides in their glass-ceramic phases, have been measured at different temperatures (80–450K) and frequencies (200–10000Hz) ranges. Though the temperature variations of ε′ and ε″ of these Pb-doped glasses do not show any peak within the frequency range of our investigation, the imaginary parts (M″) of the dielectric modulus (M″) show peaks that indicate Debye-type dielectric relaxation behaviour with a distribution of relaxation times, as suggested by the behaviour of the Cole-Cole plots. This property of ε′ and ε″ is found to be common to all the multicomponent Bi-Sr-Ca-Cu-O type glasses, which become high-T _c superconductors in their corresponding crystalline phases. The relaxation behaviour is thermally activated in nature. These glasses are also very suitable for drawing wires which become superconductors in their glass-ceramic phases.