Anomalous structure of nanocrystallites of rare-earth compounds produced by sol-gel methods

摘要

Unusual two-phase state is discovered in nanocrystallites of simple rare-earth oxides Lu_2O_3, Gd_2O_3, Y_2O_3, La_2O_3 and Eu_2O_3, garnet Y_3Ga_5O_(12) and Na_5Lu_9F_(32) at first stages of their formation. X-ray diffraction investigations have shown that both these phases are isomorphous and are realized in the same crystallite. It is concluded that over early nanocrystallization stages nanograins consist of surface- and core-phases and that the surface-phase has a larger lattice parameter, compared to the core-phase parameter. Unlike the afore mentioned cubic structures nanograins of orthorhombic LuF_3 are plate like at first stages of their formation and have the surface-phase with continuously changing in-terplanar distance from the outer developed face into the inner part.