Studies on the thermal dehydration behavior of Ln[Fe(CN) 6]· nH 2O (Ln=La–Yb; n=4, 5) by means of controlled-rate thermal analysis and Raman spectrometry

Abstract

The dehydration processes of lanthanide hexacyanoferrates(III) n-hydrates, Ln[Fe(CN) 6]· nH 2O (Ln=La–Yb; n=4, 5) were followed by means of controlled-rate thermal analysis (CRTA), the Raman spectrometry and powder X-ray diffractometer. The dehydration of the pentahydrates took place through four stages. The first, second, third and fourth stages were confirmed to correspond to the dehydrations of 1, 2, 1 and 1 mol of water molecules, respectively. The first stage corresponds to the dehydration of 1 mol of coordinated water molecules, the second stage corresponds to the dehydration of 2 mol of lattice water molecules, and the third and fourth stages correspond to the dehydration of 1 mol of coordinated water molecules, respectively. The dehydration of the tetrahydrates took place through three stages. The first, second and third stages of tetrahydrates were similar to the second, third and fourth stages of the pentahydrates. The activation energies for these stages were obtained from the CRTG curves.