Preparation of nano-powders of p-type transparent conductive copper aluminum oxide by co-precipitation method

Nano-powders of p-type transparent conductive copper aluminum oxide (CAO) have been successfully synthesized by co-precipitation method. By adding sodium hydroxide into the mixed solution of copper chloride and aluminum chloride, co-precipitate precursors of CAO with particle size around 50–60 nm were produced After washing, filtering, and drying of the co-precipitates, nano-powders of CuAlO
2
were produced when the dried co-precipitate precursors were calcined at temperature above 1100 °C. By aging at pH=3.5 for six hours and co-precipitating at pH=8.0, the atomic ratio of Cu/Al of the nano-powders can be maintained throughout the synthesis. After calcining at 12000 in air for 4 hours, the CAO co-precipitate precursors totally transformed into nano-powders of CuAlO
2
with crystal size around 64 urn. Continued calcining at 1200°C above 4 hours led to the decomposition of CuAlO
2
into nano-powders of CuAl
2
O
4
and volatile CuO with no significant change in crystal size. Finally, it was found that by calcining under inert atmosphere, the decomposition of CuAlO
2
could be suppressed at the expense of decreasing its crystallinity.