Preparation of ternary Bi-La and Bi-Pr oxides from polyaminocarboxylate complexes

Ternary bismuth-lanthanum and bismuth-praseodymium oxides are prepared by t hermal decomposition of precursor complexes derived from solutions containi ng polyaminocarboxylate ligands: H(4)edta, H(5)dtpa, H(4)egta and H(6)ttha. The thermal decomposition of these solid precursors is investigated by TGA . The resulting Bi-La and Bi-Pr oxides are characterized by XRD, XPS analys is and S-BET measurements. XRD reveals the formation of Bi(2-x)Ln(x)O(3) so lid solutions based on the Ruorite-like delta -Bi2O3 structure when Bi:Ln = 0.5 and Bi:Ln = 1, while a rhombohedral phase appears when Bi:Ln = 2. Surf ace contamination by hydroxyl and carbonate species increases with the Ln c ontent. Specific surface areas as high as 30 m(2)/g are obtained for the Ln -rich compositions. These results are compared with those obtained by the c eramic and citrate methods. (C) 2001 Elsevier Science Ltd. All rights reser ved.