The Effect of Al on a Red Shift in LaSi3N5:Ce3+ Phosphors

Abstract

Blue-emitting LaSi₃N₅:Ce₃₊ phosphors, with an orthorhombic structure and a P2₁2₁2₁ 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 LaSi_3−3x/4Al_xN₅:Ce₃₊ (or LaSi_3−xAl_xN_5−xO_x:Ce₃₊) solid solution was obtained with the well-defined P2₁2₁2₁ 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.