Search

(Y0.95Tb0.05)2O2CO3nanoparticles have been synthesized by subambient homogeneous reduction using alkalide solutions and subsequent oxidation. As synthesized, the material consists of free flowing agglomerates of ill-defined, amorphous, or subnanocrystalline nanoparticles. Thermal analysis shows that 2.83 CO2molecules are adsorbed per Y2O3formula unit in the washed product. The samples annealed at 200 °C or greater are crystalline, consisting of agglomerated nanocrystals. The nanocrystals grow from an average of 15.3−17.6 nm, the agglomerates decrease in size, and the surface area decreases from 88 to 78 m2/g as the annealing temperature is raised from 400 to 700 °C. Annealing at 800 °C results in a phase change from the carbonate to (Y0.95Tb0.05)2O2. The crystallite size of the oxide phase increases from 21.4 to 22.6 nm, and the surface area increases from 82 to 86 m2/g as the annealing temperature is increased from 800 to 1000 °C. Transmission electron microscopy observations show that the increase in the surface area, even as the average crystallite size increases, is consistent with the breaking up of agglomerates and the creation of a highly textured material, probably due to the release of CO2during the phase transition. The washed unannealed product displays luminescence typical of the Tb3ion. The photoluminescence intensity of the green 5D4−7F4transition increases with increasing annealing temperature, from 5% for the unannealed product to 16% for the nanophosphor annealed at 1000 °C. [ABSTRACT FROM AUTHOR]