Abstract

The structure of zinc-substituted nickel hydroxide is investigated as a function of the amount of zinc. The hydroxide shows a β-type structure with up to 10% zinc in substitution for nickel (in mol), whereas an α-type phase is stabilised with 20–50% zinc. For the β-type phases, the unit cell parameters are similar to those of the non-substituted phase. The X-ray diffraction patterns evidence the presence of stacking faults. Zinc cations are located in octahedral sites of the slab in substitution for nickel. For the α-type phases (d_interslab = 8.4 Å), EXAFS spectroscopy gives evidence that the zinc cations are located in tetrahedral sites of the interslab space, these tetrahedra share one face with the octahedral vacancies within the slab. Mass spectrometry coupled with thermogravimetric analysis together with chemical analysis show the presence of carbonate ions in this phase. These anions are monodendate as evidenced by IR spectroscopy. The existence of pairs of zinc cations located above and below the octahedral vacancies of the slab can be considered. This implies an excess of positive charge which is compensated by the intercalation of carbonate ions. However, the turbostratic character of the α-type phase allows the coexistence of other local configurations within the structure.