Preparation and optical properties of nanocrystallites of RE₂Sn_2−xB′_xO₇ (RE = Sm, Ce; B′ = Fe, Co, Ni; 0.0 ≤ x ≤ 1.0)

New pyrochlore-type rare-earth-complex oxides of nanometer size and with B-site dopants, RE₂Sn_2−xB′_xO₇ (RE = Sm, Ce; B′= Fe, Co, Ni; 0.0 ≤ x ≤ 1.0), have been prepared by the nonalcoholate sol-gel method. The range of average particle size is from 25 to 30 nm. It is found that this method can lower the reaction temperature (about 500 K) and shorten the reaction time. The crystal structures of these nanocrystallites belong to the cubic system, and their lattice parameters are linearly related to the content of the dopant ions. The IR spectra of these nanocrystallites were investigated, and the excitation and emission spectra for these systems show that the luminescent intensities of RE³⁺ become weaker with the iron-group dopant in the order of Fe, Co, and Ni.