Abstract
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.
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