Order-disorder transition in the Nd2−yYyZr2O7 system: Probed by X-ray diffraction and Raman spectroscopy

A series of compositions having the general formula Nd_2−yY_yZr₂O₇ have been synthesized by heating of mixtures of oxides of the components cation and characterized by X-ray diffraction and Raman spectroscopy. Rietveld analysis on the XRD data of all the compositions has been performed which revealed a decrease in lattice parameter as a function of y in the series Nd_2−yY_yZr₂O₇ (y=0.0-0.8). Subsequently, a biphasic region starts which continues for y=1.2 and 1.6. The other end member, i.e. Y₂Zr₂O₇ is found to be defect fluorite. On the other hand, Nd³⁺ has been used as surrogate material for Am³⁺, which is a minor actinide found in spent nuclear fuel. In the pyrochlore range, the increasing trend of the x-parameter of 48f oxygen indicates the enhancement of disorder in the system. Raman spectroscopy has been employed to validate the data obtained from XRD. The involvement of 48f oxygen in disorder has also been verified by Raman spectroscopic investigation.