Cation substitution induced excellent quantum efficiency and thermal stability in (Ca1−xSrx)9La(PO4)7:Eu2+ phosphors†
Stable and efficient inorganic single-doped (Ca1−xSrx)9La(PO4)7:Eu2+ (0 ≤ x ≤ 1) phosphors were demonstrated. Color-tunable photoluminescence behavior dependent on the bimodal-cation was approached by adjusting the A site. With the incorporation of Sr2+ into Ca9La(PO4)7:Eu2+, the phase transition occurred from R3c to Rm. Thus, the relationships between the structural and photoluminescence properties are studied. The emission color changed from yellowish-green to blue across the white light region at an excitation wavelength of 360 nm. The internal quantum efficiency (QE) was found to reach 36%, 28%, 35%, 30% and 100% at 360 nm excitation. The thermal stability of the photoluminescence of CLP:Eu2+ and SLP:Eu2+ achieved 38% and 90% at 150 °C, respectively. Single-emitting component phosphors for a new white LED system with perfect stability and color reproducibility were achieved. Stable and efficient SCLP:Eu2+ phosphor systems for white LEDs are believed to be a very important material in the application of pc-LEDs beyond the technical limitations of traditional lighting technologies.