Positive effect of high-energy ball milling on the low temperature reactivity. Solid state synthesis of CuAlO2 phase at 900 °C without regrinding procedure. Transition alumina effects on the crystallite size reduction of Cu2O down to ∼8 nm. Core–shell configuration of Cu2O nanoparticles. A unique weak ferromagnetic feature of CuAlO2 associated with the structural paramagnetic Cu2+ and Fe3+ ions.