HOPPING TRANSPORT IN THE PRECURSOR GLASSES OF THE SUPERCONDUCTING SYSTEM BI-SR-CA-CU-O

The first measurement is reported for the electrical properties of the precursor glasses in the high-temperature superconducting system Bi-Sr-Ca-Cu-O. The phonon-assisted hopping of small polarons is consistent with the DC conductivity in the high temperature region; however, at lower temperatures a variable range hopping mechanism dominates the conductivity. The correlated barrier hopping model is consistent with the temperature and frequency dependence of the AC conductivity and its frequency exponent.