Optical and Electrical Properties of Mechanochemically Synthesized Nanocrystalline Delafossite CuAlO₂

Nanocrystalline p-type semiconductor copper aluminum oxide (CuAlO₂) has been synthesized by mechanical alloying using freshly prepared Cu₂O and α-Al₂O₃ nanocrystals in toluene medium. A study on structural property performed with different alloying and post annealing durations, by X-ray diffraction (XRD) reveals the formation of single phase with average crystallite size ∼45 nm. Optical absorbance onset at 364.5 nm confirms its wide band gap nature (E _g = 3.4 eV) and the fluorescence emission behaviour (390 nm) confirms its direct band type transition. The activation energy for electrical conduction has been calculated by Arrhenius plots using impedance measurement. Both grain and grain boundary conductivity takes place with almost equal activation energies of ∼0.45 eV. The paper discusses synthesis, structural, optical and electrical properties of delafossite CuAlO₂ in detail.