INFRARED CHARACTERIZATION OF TURBOSTRATIC ALPHA-COBALTED AND WELL CRYSTALLIZED ALPHA-STAR-COBALTED NICKEL HYDROXIDES

Substitution of at least 20% of trivalent cobalt for nickel leads to alpha- and alpha*-nickel hydroxides which are stable in KOH. The compensation of the excess of positive charge results from the insertion of anions (CO32- or SO42-) in the van der Waals gap. The IR study shows that these anions are in D3h and T(d) symmetries, respectively, while the adsorbed ones are linked to the transition elements (C2v and C3v symmetries, respectively). This study also confirms the stability of alpha* Co3+- and alpha-Co3+-hydroxides in concentrated KOH solution, and the instability of alpha-Co2+ ones which leads to the formation of beta-Co3+-hydroxides.