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, La(4)PdO(7) along with a trace of oxides of palladium and lanthanum at 1000 degrees C. The generation of several unstable intermediate phases at different temperatures was attributed. The mixed metal oxides, La(4)PdO(7) and La(2)Pd(2)O(5) along with oxycarbonate and oxide of lanthanum were identified at 1000 degrees C in case of tartrate precursor. The carbides of lanthanum and elemental carbon were also generated at the end in both the precursors. The Delta H# and Delta S# of all the steps up to 500 degrees C of the precursors are explored from DSC study in nitrogen. (C) 2008 Elsevier B.V. All rights reserved.