The conductivity of alloyed radical anion salts : 2,5-disubstituted DCNQI's with copper-counterions

Abstract
We have performed conductivity measurements on a series of binary and ternary copper-salts from differently substituted R, R' — N, N'-dicyano-quinonediimines (DCNQI's ). At room temperature they all have a high conductivity, which is preserved partly down to the lowest temperatures. In comparison with the (unalloyed) single complex crystals in these alloys disorder effects shift phase transition temperatures and reduce the magnitudes of the conductivity. In two cases dips of the T-dependent conductivity appear below 50 K. They are explained by a metal-semiconductor transition accompanied by a reentrance into the metallic state at even lower temperatures, in analogy to similar results on (2,5-Me, Me-DCNQI)2Cu under applied pressure