Lanthanide effect on the formation and evolution of nanocrystalline structures in Ln(2)Hf(2)O(7) compounds (Ln = Sm-Dy)

摘要

X-ray diffraction with synchrotron radiation has been used for comparative analysis of crystal structure evolution in Ln(2)Hf(2)O(7) (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 600-700A degrees C initiates the formation of nanocrystallites with a fluorite structure. Long-range cationic ordering of the pyrochlore type appears in Ln(2)Hf(2)O(7) (Ln = Sm-Tb) samples once a definite crystal size has been achieved at temperatures a parts per thousand yen1200A degrees C. In Dy2Hf2O7 samples, a defect fluorite structure persists in the entire range of heat-treatment temperatures.