Doping effect on electronic transport properties of Sr14(Cu1−yMy)24O41 (M=Zn, Ni)

Polycrystalline samples of Sr14(Cu1−yMy)24O41 (M=Zn/Ni) were prepared by conventional solid-state reaction. The series of samples up to y⩽0.05 are identified to be single phase and no regular shift of lattice parameters a, b, c is found. The measurements of electronic transport show that although the doping compounds are still semiconductive as the parent phase, Zn and Ni dopants induce a decrease of electrical resistivity. Furthermore, Zn doping depresses the resistivity more significantly than Ni doping. A crossover temperature Tρ that exhibits in the Arrhenius plot of the resistivity versus temperature is observed in all the samples and goes up with the increase of the dopants. The origin of the decrease in resistivity with doping and the conduction mechanisms both above Tρ and below Tρ are discussed.