An investigation on the solid-state thermal decomposition of bimetallic oxalate and tartrate coordination precursors of lanthanum(III) and palladium(II) ions

The bimetallic oxalate and tartrate coordination precursors, palladium(II)tris(oxalato)lanthanate(III)heptahydrate (POL) and palladium(II)tris(tartrato)lanthanate(III)pentahydrate (PTL) have been synthesized and their thermal behaviors were explored. The precursors were characterized by elemental analysis, IR, electronic spectral and X-ray powder diffraction studies. The solid-state thermal decomposition studies (TG, DTG and DTA) in air revealed that the oxalate precursor led mainly to a mixed metal oxide, La4PdO7 along with a trace of oxides of palladium and lanthanum at 1000 °C. The generation of several unstable intermediate phases at different temperatures was attributed. The mixed metal oxides, La4PdO7 and La2Pd2O5 along with oxycarbonate and oxide of lanthanum were identified at 1000 °C in case of tartrate precursor. The carbides of lanthanum and elemental carbon were also generated at the end in both the precursors. The ΔH# and ΔS# of all the steps up to 500 °C of the precursors are explored from DSC study in nitrogen.