Synthesis and electrical conductivity of RECuO_(2+d) (RE chemical bounds Y, La, Pr, Nd, Sm and Eu) delafossite

摘要

The structural and electrical properties of layered cuprates of a RECuO_2 delafossite structure have been investigated with various rare earth elements (RE chemical bounds Y, La, Pr, Nd, Sm and Eu). A new delafossite-derived phase, i.e. oxygen-rich RECuO_(2+ delta ) ( delta => 0.5) previously reported by Cava et al. for YCuO_(2+ delta ) and LaCuO_(2+ delta ) was found in all the RECuO_2 systems studied. Each as-sintered RECuO_2 sample appeared to have a nearly stoichiometric oxygen content, but by annealing under oxidizing conditions excess oxygen corresponding to approx 0.6 atoms per formula unit could be loaded into the structures. Although electrical resistivity of the as-sintered RECuO_2 sample was quite high of > 10~5 OMETA cm at room temperature, i.e. corresponding to an almost insulating behavior, all the samples became conductive by introducing the excess oxygen.