Large-scale production of spherical Y₂O₃:Eu³⁺ phosphor powders with narrow size distribution using a two-step spray drying method

A simple strategy to prepare dense spherical Y₂O₃:Eu³⁺ phosphor particles with a narrow size distribution is proposed, using two steps of spray drying carried out with a commercially available spray dryer. The key idea is first to prepare hollow Y₂O₃:Eu³⁺ precursor particles by spray drying an aqueous precursor solution containing citric acid. Thereafter, nanosized particles are obtained from the precursor powders by simple ball milling and dispersed in water to form a colloidal suspension that is spray dried, forming porous granules of dense spherical nanoparticles. Next, highly crystalline Y₂O₃:Eu³⁺ is obtained by sintering the granules at temperatures above 1200 °C. The resulting Y₂O₃:Eu³⁺ particles are spherical and are shown to have good luminescence properties as a red phosphor. The feasibility of the strategy proposed here is proved experimentally.