K7Ca9[Si2O7]4F:Ce3+: a novel blue-emitting phosphor with good thermal stability for ultraviolet-excited light emitting diodes

Abstract

In this work, a novel potassium-calcium silicate-fluoride based phosphor: K₇Ca₉[Si₂O₇]₄F (KCSOF) has been successfully synthesized by a solid-state reaction at low temperature. The occupation of Ce³⁺ is studied by Rietveld refinement, luminescence properties and decay curves. KCSOF:Ce³⁺ presents a wide absorption band ranging from 240 to 420 nm and displays blue emission (λ_max = 445 nm). Good thermal stability has also been detected, which shows that it still retains 90% of the initial intensity at 200 °C. In addition, a white LED device has been manufactured by connecting a 380 nm UV chip with a blend of KCSOF:Ce³⁺, (Sr, Ba)SiO₄:Eu²⁺ and CaAlSiN₃:Eu²⁺. The color coordinates, correlated color temperature and color rendering index of the manufactured LED device are (0.421, 0.407), 3256 K and 95.55, respectively. These results suggest that the blue-emitting KCSOF:Ce³⁺ phosphor has good prospects for applications in white UV LEDs.