Characterisation of new hybrid organic-inorganic nickel silicates by polarised EXAFS

The angular dependence of the X-ray absorption coefficient (P-EXAFS) has been used in order to characterise the local order, around the metallic cation, in two lamellar nickel silicates, with Ni/Si = 3/2 or 3/1. The aim of this study is to get insight into the local environment of Ni2+ cations concerning the first and second shells. The first neighbours are oxygen in octahedral arrangement, with a flattening angle of 59degrees or 60degrees for the two studied compounds. The second shell consists in 6 Ni, as expected for trioctahedral hydroxide layer and 2 Si grafted to the layer. From the evolution of Si coordination with the incident angle of the X-ray beam, Si are grafted with a random orientation and not only rigorously perpendicularly to the layers, as can be observed in clay materials. (C) 2002 Elsevier Science B.V. All rights reserved.