Crystal Structure and Superconductivity of Tetragonal and Monoclinic Ce1-xPrxOBiS2

Ce1-xPrxOBiS2 powders and Ce0.5Pr0.5OBiS2 single crystals were synthesized and their structure and superconductive properties were examined by X-ray diffraction, X-ray absorption, electronic resistivity, and magnetization. While PrOBiS2 was found to be in a monoclinic phase with one-dimensional Bi S zigzag chains showing no superconductive transition above 0.1 K, CeOBiS2 was in a tetragonal phase with two-dimensional Bi S planes showing zero resistivity below 1.3 K In the range x = 0.3-0.9 in Ce0.5Pr0.5OBiS2, both monoclinic and tetragonal phases were formed together with zero resistivity up to a maximum temperature of 2.2 K. A Ce0.5Pr0.5OBiS2 single crystal, which showed both zero resistivity and a decrease in magnetization at 2.4 K, presented a tetragonal structure. Short Bi S bonding in flat two-dimensional Bi S planes and mixed Ce3+/Ce4 were characteristic features of the Ce0.5Pr0.5OBiS2 single crystal, which presumably triggered its superconductivity.