Crucial role of the reaction conditions in isolating several metastable phases in a Gd-Ce-Zr-O system.

A series of samples with composition Gd(2-y)Ce(y)Zr(2)O(7) (0.0 ≤ y ≤ 2.0) were prepared by the gel combustion method followed by high-temperature reduction. The details of the structural variations as a function of the composition, temperature, and oxygen stoichiometry have been investigated by X-ray diffraction (XRD), high-temperature XRD (HT-XRD), and thermogravimetry. A complete solubility of Gd(3+) in Ce(2)Zr(2)O(7) and Ce(2)Zr(2)O(8) could be achieved by this adaptive preparative method. Analysis of the XRD data revealed a sequential variation of the structural features with oxygen stoichiometry as well as Gd(3+) contents in these compositions. The variation in the unit cell parameter along the compositions has a strong influence on the oxygen uptake behavior in the Gd(2-y)Ce(y)Zr(2)O(7) system, as observed from the thermogravimetric and HT-XRD studies. The preparation and stability of various metastable phases in Gd-Ce-Zr-O have been addressed in detail. The details of the study will be useful for the design and application of a potential redox catalyst and an oxygen storage capacitor.