Structural and transport properties of CuSc1-xMgxO2+y delafossites

Transport and structural properties of Mg-doped and O-intercalated sintered powders and polycrystalline films of CuSc1-xMgxO2+y are reported. Substitution of Mg for Sc systematically increases the p-type conductivity in CuSc1-xMgxO2 sintered powders, producing a maximum conductivity of 0.015 S/cm at xapproximate to0.06. A similar level of conductivity is observed in transparent polycrystalline CuSc1-xMgxO2 films at the same doping level. Mg doping causes no significant increase in optical absorption at this level. Intercalation of oxygen into the delafossite structure leads to a much larger increase in p-type conductivity. In powders, the maximum conductivity is 0.5 S/cm at y=0.23 and x=0.05. In oxygen-intercalated films, the maximum conductivity was 25 S/cm, with the transparent films gradually darkening as oxygen is incorporated. Oxygen intercalation increases the a-axis lattice parameter of the delafossite structure in both films and powders, with a much smaller effect on the c-axis parameter. Two distinct phases with yapproximate to0 and yapproximate to0.5 are observed in x-ray diffraction of powders. In films intermediate values of y are observed, often in combination with a distinct y=0 phase. The absorption properties of the powder samples indicate introduction of defects into the 2H polymorph of CuScO2 and CuSc1-xMgxO2 compared to the 3R polymorph. (C) 2004 American Institute of Physics.