Ce3+-doped beta-SiAlON oxynitride blue phosphors with a composition of CexSi6-zAlzOzN8-z (x = 0.005-0.050 and z = 0.25) were synthesized by sintering with gas pressure. Phase purity, microstructure, valence state of Ce ions, and photoluminescence properties were studied. The prepared beta-SiAlON:Ce3+ revealed strong excitation peaks in the near-UV spectral region and intense broad-band blue emissions in the range 470-490 nm. The effects of Ce3+ doping concentration and temperature dependence on the photoluminescence properties were investigated as well. These experimental results clearly proved that beta-SiAlON: Ce3+ is a good candidate for down-conversion blue phosphor in the application of a UV light emitting diode (LED). (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3269047] All rights reserved.