Thermal behaviour of the copper-substituted cobalt hydroxide fluoride series CuxCo1−x(OH)F

The basic salt cobalt(II) hydroxide fluoride was obtained by partial hydrolysis of a 0.2M solution CoF₂. Mixed Co(II)·Cu(II) hydroxide fluorides with an isomorphic substitution of Co(II) by Cu(II) ions up to 20% were also prepared. XRD data obtained on these compounds indicate that they are single-phase compounds, their X-ray powder patterns being almost identical to the Co(OH)_0.7F_1.3 diagram, with Zn(OH)F-type structure. However, their stoichiometries are very close to Co_1?xCu_x(OH)F (0≤x≤0.2). Thermal analysis studies carried out up to 1273 K in still air or under dynamic vacuum conditions show that in air CoO or a mixture of CoO and CuO is formed as final product. In vacuum, at high temperature, with a Ta heating surface, pure α-Co or a mixture of α-Co and Cu is formed at about 973 K.