Cobalt aluminate CoAl 2 O 4 powder, constituted of nano-sized crystallites, is prepared, involving the reactivity of AlCl 3 and CoCl 2 with molten alkali-metal nitrates. The reaction at 450 °C for 2 h leads to a mixture of spinel oxide Co 3 O 4 and amorphous γ-Al 2 O 3 . It is transformed into the spinel oxide CoAl 2 O 4 by heating at 1000 °C. The powders are mainly characterized by XRD, FTIR, ICP, electron microscopy and diffraction, X-EDS and diffuse reflection. Their properties are compared to those of powders obtained by solid state reactions of a mechanical mixture of chlorides or oxides submitted to the same thermal treatment.

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