Blue-emitting LaSi3N5:Ce3+ phosphors, with an orthorhombic structure and a P2(1)2(1)2(1) symmetry, could be used for UV chip-based white light emitting diodes (WLED). However, the application of these phosphors to WLEDs has been restricted because of an unsatisfactory excitation efficiency in the wavelength range that is used by most WLED applications to pump phosphors. Al was introduced into LaSi3N5:Ce3+ to facilitate a single-phase synthesis and to red-shift the excitation band toward a desirable wavelength region. As a result, a single-phase LaSi3-3x/4AlxN5:Ce3+ (or LaSi(3-x)Al(x)N(5-x)Ox:Ce3+) solid solution was obtained with the well-defined P2(1)2(1)2(1) structure maintained. The red shift was attributed to the enhanced centroid shift and to a reduced Ce-N bond length caused by the Al inclusion. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3579505] All rights reserved.