HOPPING CONDUCTIVITY IN RBA2CU2COOY (R=Y AND PR)

We report measurements of room-temperature lattice parameters and resi stivity (rho) up to 300 K, of single phase, maximally oxygenated ceram ic samples of RBa2Cu2CoOy (R = Y, Pr). In both sets of samples, the re sistivity up to room temperature follows the Mott variable-range-hoppi ng (VRH) law rho = rho(o)exp(T(o)/T)1/4. The results obtained in this work are compared with previously obtained results on samples belongin g to the ''1-2-3'' family and related compounds, where activated hoppi ng is the dominant conduction mechanism. We propose a general relation between the experimental parameters. Potential applications of these materials are discussed.