Some polynuclear coordination compounds precursors of chromites - Synthesis, physicochemical characterization and thermal stability

The polynuclear coordination compounds LnCr(tartrate)(3). nH(2)O where Ln(I II)=La-Er, obtained through a precipitation method, were characterized on t he basis of elemental analysis, their electronic and vibrational spectra an d magnetic susceptibility measurements. The possibility of obtaining chromi tes through the transformations of the polynuclear coordination compounds i n the solid state was considered. The thermal decompositions of these compo unds, studied by TG and DTA methods, were found to follow an almost uniform pattern. The decompositions occurred in six-eight steps. The first two ste ps involved dehydration, and the third the transformation of tartrate anion s to oxalate, followed by conversion to carbonate and oxocarbonate intermed iates. The final product in each case was LnCrO(3). A non-isothermal kineti c analysis of the first decomposition steps was performed, the most probabl e decomposition mechanism being selected and the kinetic parameters evaluat ed. The final products of the transformations were characterized.