摘要:
Yttrium-based multimetallic oxides containing bismuth and/or niobium were prepared by a method starting from pre-isolated stable water-soluble precursors which are complexes with the ethylenediaminetetraacetate ligand (edta). The cubic Bi1-xYxO1.5 (x = 0.22, 0.25 and 0.3) and Y3NbO7 oxides were obtained in a pure form in a range of moderate temperatures (600-650 degrees C). This preparation method also allowed to stabilize at room temperature, without quenching, the tetragonal YNbO4 oxide in a distorted form (T'-phase) by calcining the precursor at 800 degrees C. When heated up to 1000 degrees C, this metastable T'-phase transforms into the metastable "high-temperature" T oxide, which converts on cooling down to room temperature into the thermodynamically stable monoclinic M oxide. Doping the YNbO4 oxide with Bi3+ cations (0.5% and 1% Bi with respect to total Bi + Y amount) led at 800 degrees C to a mixture of the T'-phase and the thermodynamically stable monoclinic one. At 900 degrees C, the almost pure monoclinic structure was obtained. (c) 2007 Elsevier Inc. All rights reserved.