Pr2M2O7 (M=Zr, Hf) local and crystal structure changes in a fluorite-pyrochlore phase transition.

2nd Conference on Plasma & Laser Research and Technologies

Menushenkov, A.P.^1 ; Popov, V.V.^1,2 ; Gaynanov, B.R.^1 ; Zubavichus, Ya V.^2

National Research Nuclear University MEPhI, Moscow Engineering Physics Institute, Kashirskoe sh. 31, Moscow

115409, Russia^1

NRC, Kurchatov Institute, pl. Akademika Kurchatova 1, Moscow

123182, Russia^2

关键词: Amorphous precursors;    Annealing temperatures;    Calcination temperature;    Debye Waller factor;    Nanocrystal powders;    Oxygen coordination;    Pyrochlore structures;    Pyrochlore-type structure;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/747/1/012038/pdf
DOI  :  10.1088/1742-6596/747/1/012038

来源: IOP

【 摘 要 】

The formation of nanocrystal powders of Pr2M2O7(M=Zr, Hf) compounds upon calcinations up to 1400°C has been investigated by using of X-ray absorption fine structure (XAFS) spectroscopy combined with X-ray powder diffraction (XRD). The structure ordering upon calcination was estimated independently from XRD and EXAFS data. It was found that the phase transition fluorite-pyrochlore occurs at calcination temperature in the range of 900-1000°C. The appearance of the ordered pyrochlore structure at calcination temperatures above 1000°C was manifested as splitting of the first oxygen coordination shell of the local praseodymium environment and supported by a sharp reduction of the Debye-Waller factor values of interatomic bonds. Besides we observed the L3-Hf X-ray absorption near edge line shape splitting with increasing of annealing temperature of amorphous precursor due to crystal field influence in high ordered pyrochlore-type structure.