A One-Step Ultrasonic Spray Pyrolysis Approach to Morphology-Controlled Synthesis of Hollow and Porous YBO₃:Eu³⁺...

YBO₃:Eu³⁺ phosphors are regarded as strong candidates for high-performance luminescent materials owing to their excellent luminescence efficiency. In this study, novel YBO₃:Eu³⁺ porous/hollow microspheres were synthesized via a simple, continuous ultrasonic spray pyrolysis (USP) process using different organic additives. XRD analysis confirms that all samples crystallize in a pure hexagonal YBO₃ phase, indicating that the additives do not affect phase formation. Electron microscopy reveals a clear morphological evolution from solid to porous and hollow microspheres, with tunable shell thickness and cavity size. Compared with solid microspheres, the obtained hollow microspheres significantly reduce the consumption of rare earth materials with minimal influence on luminescence properties. The results suggest that hollow microspheres are promising substitutes for solid microspheres in the field of rare earth phosphors and the ultrasonic spray pyrolysis (USP) approach shows great potential in large-scale synthesis of morphology-controllable microspheres.