Nd and Ce simultaneous substitution driven structure modifications in Gd2−xNdxZr2−yCeyO7

Single phase Gd2−xNdxZr2−yCeyO7 (0 ≤ x, y ≤ 2) ceramics were synthesized by a simple solid-state reaction method. The neodymium and cerium simultaneous substitution influence on the structure modifications were first investigated systematically. X-ray diffraction has been utilized to confirm adoption of pyrochlore or fluorite structure. XRD results show that structure modifications induced by simultaneous substitution are strongly dependent on the solubility of both Nd and Ce. It was found that the ordered pyrochlore structure was maintained for samples with 1.6 ≤ x ≤ 2, 0 ≤ y ≤ 0.4, from Gd0.4Nd1.6Zr2O7 to Nd2Zr1.6Ce0.4O7. Whereas, the ordered pyrochlore structure was lost for samples with 0 ≤ x ≤ 2, 0.8 ≤ y ≤ 2, from Gd2Zr1.2Ce0.8O7 to Nd2Ce2O7, and the structure transformed to fluorite. Furthermore, at the Gd3+ and Zr4+ positions, the whole of Gd3+ and Zr4+ could be replaced by Nd3+ and Ce4+, respectively, with its end member Nd2Ce2O7 was fluorite structure. The studies established the existence of a continuous range of Gd2−xNdxZr2−yCeyO7 (0 ≤ x, y ≤ 2) ceramics with a single phase structure.