Evidence for variable-range hopping in semiconducting rare-earth-Ba-Cu-O

Abstract
The authors have measured the electrical conductivity of semiconduction RE-Ba-Cu-O (RE=Y, La, parasite) samples and have found a fairly good agreement with a ln sigma approximately (T0/T)1/4 law of variable-range hopping except for the Y-containing compounds. The range of validity of this behaviour extends from room temperature down to about 80 K. The values for T0/sup /lie between 104 and 107 K.