LAYER RIGIDITY IN 2D DISORDERED NI-AL LAYER DOUBLE HYDROXIDES

A series of layer double hydroxide carbonates with the chemical composition [(CO3)(x/2).y(H2O)]-[Ni1-xAlx(OH)(2)], O < x < 0.4, 0 < y < 1.2 has been prepared. The composition dependence of the basal spacing of these compounds has been determined from X-ray diffraction measurements and has been computed using an extended version of the discrete finite-layer rigidity model which includes both intra- and inter-layer rigidity effects. The inter- and intra-layer rigidity parameters of Ni(OH)(2) were found to be similar to 5 and 2.44, respectively, from which we conclude that the host Ni(OH), spans class II and class III layered solids. On the basis of our X-ray measurements and steric considerations, it is determined that the carbonate ion is oriented in the host gallery with its threefold axis essentially parallel to the host c-axis.