Thermal behavior of a zinc-chromium-sulfate lamellar double hydroxide revisited as a function of vacuum and moisture parameters

Lamellar Double Hydroxides (LDHs) intercalating XO42− oxo-anions show particular behaviors related to moisture and temperature parameters. In this paper we study the evolution of a [Zn-Cr-SO4] phase as a function of vacuum treatment by in situ XRPD under non-ambient conditions, water vapor pressure control and thermal treatments. A specific experimental device was developed in order to perform the measurements. Several kinds of structural modifications are evidenced: progressive evolutions of the lattice parameters as well as discrete transformations resulting from rearrangements in the interlayer domains. The layered host structure is maintained with different basal spacings in 7-11 Å range. The nature of these transformations and their reversibility are discussed.