Lanthanide effect on the formation and evolution of nanocrystalline structures in Ln2Hf2O7 compounds (Ln = Sm-Dy)
X-ray diffraction with synchrotron radiation has been used for comparative analysis of crystal structure evolution in Ln2Hf2O7 (Ln = Sm-Dy) complex oxides with a fluorite-pyrochlore structure, synthesized by isothermal annealing of mixed hydroxides. It has been shown that heat treatment of the precursor in the temperature range 600–700°C initiates the formation of nanocrystallites with a fluorite structure. Long-range cationic ordering of the pyrochlore type appears in Ln2Hf2O7 (Ln = Sm-Tb) samples once a definite crystal size has been achieved at temperatures ≥1200°C. In Dy2Hf2O7 samples, a defect fluorite structure persists in the entire range of heat-treatment temperatures.
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