Copper aluminium oxide($CuAlO_2$) particles, a promissing p-type TCO(transparent conducting oxide), were prepared by the spray pyrolysis. The preparation conditions were investigated by changing precursors, preparation temperature and annealing temperature. Delafossite phase of $CuAlO_2$, which exhibits TCO characteristics, was obtained when copper nitrate, copper acetate and copper sulfate, divalent copper precursors, were used as copper precursors and aluminium nitrate as aluminium precursor. The annealing process at 1100 ℃ converted the as-prepared particles to copper aluminate delafossite. Copper aluminate doped oxygen were prepared to achieve higher conductivity. In the solid-state reaction, post-treatment with $O_2$ decomposed $CuAlO_2$ to $CuAl_2O_4$ and CuO. In this work, paricles prepared by using different oxygen flow rate in carrier gas for oxygen doping. The highest conductivity achieved by using $O_2$, 3 l/min and $N_2$, 1 l/min as carrier gas was 7 times higher than that of the non-doping $CuAlO_2$ prepared by the spray pyrolysis and 3 times higher than that of the non-doping $CuAlO_2$ prepared by the solid-state reaction.
To improve the conductivity, Cd, Mg, Sr and Zn were tested as cationic dopant. The conductivity increased with the amount of Cd addition, and decreased after Cd loading was over 7 at.%. The other species changed the crystalline structure of particles. Only the cadmium turned out to be effective for improving conductivity.
