Thermal and structural changes of lanthanum hexacyanocobaltate(III) pentahydrate, La[Co(CN)(6)]. 5H(2)O were investigated by means of thermal analysis, visible electronic spectra, IR, powder X-ray diffraction, EXAFS and TG-MS. The dehydration of La[Co(CN)(6)]. 5H(2)O proceeded reversibly through three steps and steps corresponded to the losses of H2O, 3H(2)O and H2O, and the enthalpy changes for these steps were 51.3, 211.0 and 38.7 kJ mol(-1), respectively.
After the dehydration, the colour of the anhydride changed from white to blue around 290 degrees C and an abrupt mass loss occurred at 350 degrees C. The colour change seems to be attributable to the change of coordination geometry around the Co ions from an octahedral structure to a tetrahedral one. LnCoO(3) was obtained as a final product by heating the sample to 1000 degrees C.