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Opportunities for the synthesis of ultrafine spherical particles with uniformly distributed components and phases are of special importance when materials for photonic application are considered. In this study, the nanophase, spherical, luminescent polycrystalline Gd 2 O 3 :Eu and YAG:Ce particles were synthesized from aerosols of the corresponding nitrate solutions ultrasonically generated with frequencies of 1.7 MHz and 800 kHz, respectively. Detailed phase and structural analysis, compositional homogeneity, and particle morphology were determined in accordance to X-ray diffraction ͑XRD͒, scanning electron microscopy ͑SEM͒, and energy dispersive X-ray spectroscopy ͑EDS͒. Quantitative SEM/EDS analysis indicated high material purity and compositional homogeneity. The phase development and structural changes imply nanocrystalline inner structure ͑crystallites below 60 nm after thermal treating͒, which influences luminescence behavior. Luminescence measurements indicate that both the radioluminescence and thermoluminescence emission spectra of the Gd 2 O 3 :Eu are totally dominated by the line emission characteristic of the Eu, fully substituted onto host lattice sites. By contrast, the cerium dopants in YAG display only very weak Ce luminescence after annealing, but there are broad emission bands characteristic of host lattice defect sites. The spectra are clearly altered by heat treatments and the thermoluminescence indicates a range of independent defect emission sites.

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