Order-disorder structural transition of Nd2(Zr1-xCex)2O7 pyrochlores prepared by auto-combustion method.

A series of pyrochlore solid solutions with general formula Nd 2 (Zr 1- x Ce x) 2 O 7 were successfully synthesized by the glycine-nitrate process (GNP) auto-combustion method and then sintered at high temperature. The order-disorder structure of the as-prepared ceramic samples was systematically characterized by X-ray diffraction (XRD) and Raman spectroscopy. Rietveld refinements of the typical XRD patterns were performed using Full-prof software. XRD and Raman results confirmed a co-existence structure composed of ordered pyrochlore and disordered defect-fluorite structure for Nd 2 (Zr 0.75 Ce 0.25) 2 O 7 and Nd 2 (Zr 0.7 Ce 0.3) 2 O 7 samples. And Nd 2 Ce 2 O 7 specimen presented as defect-fluorite structure with rare earth C-type microdomains in both XRD and Raman spectroscopy. The effect of 48 f oxygen on phase transition was verified by XRD and Raman spectroscopy. The refined x -parameter of 48 f oxygen reflected the phase transition of Nd 2 (Zr 1- x Ce x) 2 O 7 solutions from pyrochlore to fluorite structure. High resolution transmission electron microscope (HRTEM) images and selected area electron diffraction (SAED) analysis of transmission electron microscopy (TEM) proved the representative Nd 2 (Zr 0.7 Ce 0.3) 2 O 7 sample showed biphasic structure with pyrochlore and defect-fluorite structure SAED rings. Also, the C-type microdomain SAED rings of Nd 2 Ce 2 O 7 structure was found by TEM analysis. [ABSTRACT FROM AUTHOR]