The monodisperse spherical SiO2/Y2O3:Tb3+ core/shell particles were prepared by a heterogeneous precipitation coating of the phosphor shell on the surface of the core particles. The shell thickness and the calculated crystallite size were increased with the core size and, thus, the photoluminescence (PL) intensity was also increased. The phosphor photonic crystals (PCs) were fabricated by self-assembly of the core/shell particles. The PL intensity of the phosphor PCs was higher by around 2.0 times than that of the randomly stacked reference sample due to the high packing density and quality. The suppression of the PL emission peaks by the overlap with the stopband and the enhancement of the emission peak at the blue edge of the stopband were observed. The color purity of the phosphor PCs was definitely improved by the design of the stopband position. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3474219] All rights reserved.