Site occupancy and photoluminescence tuning of La3Si6−xAlxN11−x/3:Ce3+ phosphors for high power white light-emitting diodes
A series of blue light excitable yellow-emitting La3Si6−xAlxN11−x/3:Ce3+ (x = 0, 0.02, 0.04, 0.06, 0.08, and 0.1) phosphors were prepared by a high temperature solid state reactions method. The variations in micro-structure and luminescent properties induced by substituting the Al3+/Si4+ ratio in La3Si6−xAlxN11−x/3:Ce3+ and the related mechanism were investigated. Interestingly, the emission spectrum displayed a red-shift by strengthening the longer wavelength component of the spectrum instead of shifting the emission peak, which was verified to be ascribed to the changed site occupancy of Ce3+. The inducement of redistribution of Ce3+ by introduction of Al3+ as well as its influence on local structures were explored. A tunable spectrum could be obtained through controlling the entering rate of Ce3+ at two different sites. The color rendering index of this phosphor system could be greatly improved with sufficient emission efficiency and thermal stability for applications in high power white light-emitting diodes.