Interconversion of brucite-like and hydrotalcite-like phases in cobalt hydroxide compounds

Formation and interconversion of cobalt hydroxides have been investigated w ith XRD, FTIR, and compositional analysis. Effects of addition time, aging time, and preparative atmosphere on phase transformation and materials synt hesis in ammoniacal solution have been systematically examined. A new precu rsor phase with hydrotalcite-like characteristics has been identified. Whil e alpha-Co(OH)(2) is prepared with short-aging in nitrogen atmosphere, this divalent metal (Co2+) hydrotalcite-like phase transforms into brucite-like beta-Co(OH)(2) under prolonged aging in nitrogen. The beta-Co(OH)2 can be formed readily in air but later is converted into a new hydrotalcite-like p hase which is stable and contains both Co2+ and Co3+ due to redox reactions . Interconversions among the four structural phases have been investigated and correlated.