| Abstract
| - Supported by X-ray absorption and Mössbauer observations, layered double hydroxides (LDH) synthesized in the presence of tetravalent cations (Sn4+ and Zr4+) give rise to a phase segregation: LDH with the cell parameters following a divalent−trivalent cation substitution and an amorphous coating of the tetravalent cation oxide presenting a local order similar to SnO2 and ZrO2, respectively.
- The incorporation of tetravalent cations (Zr4+ and Sn4+) inside sheets of layered doublehydroxide (LDH) was reported by Velu et al. As no local structural information was providedso far, the question here is whether the LDH structure may accommodate such a presence.From three different systems presenting the cation compositions MgAlSn, MgAlZr, andCoAlSn, we provide (by means of X-ray absorption and Mössbauer spectroscopies) clearevidence that the tetravalent cations are segregated from the LDH structure and formamorphous MIV oxide-like particles. Variation of the cell parameters, a and c, is thenexplained by a substitution of Al cations by the divalent cations, MII. It is also shown thatdespite the fact that the process of reconstruction occurs for MgAlM (M = Zr and Sn), thetetravalent cations do not participate in this structural recovery.
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