Multiple site occupancy induced a novel broadband Ca8(Al12O24)(WO4)2: Eu2+ blue phosphor for pc-WLEDs
摘要
A series of novel broadband blue-emitting Ca8(Al12O24)(WO4)2: x% Eu2+ (0.1≤x≤2.5) phosphors were synthesized via the solid-state method. The analysis of crystal structure and the X-ray diffraction confirms that the Ca8(Al12O24)(WO4)2: Eu2+ phosphors are phase-pure and crystallize in the orthorhombic system with space group Aba2. The wide bandgap energy of the Ca8(Al12O24)(WO4)2 host provides a suitable bandgap environment for Eu2+ ions. Under 325 nm excitation, the Ca8(Al12O24)(WO4)2: Eu2+ exhibits a broad blue-emitting band in the range of 380–550 nm, resulting from the 4f65d1→4f7 transition of Eu2+. As the concentration of Eu2+ increases, the emission peak of Ca8(Al12O24)(WO4)2: Eu2+ undergoes a redshift, originating from the site competition by Eu2+ doping. Concurrently, due to concentration quenching, the emission intensity initially increases and subsequent decreases, reaching a maximum at an optimal Eu2+ doping concentration of 0.3%. The concentration quenching mechanism was confirmed to be electric dipole-dipole interaction. Additionally, the optimally doped Ca8(Al12O24)(WO4)2: 0.3% Eu2+ phosphor exhibits bright blue emission with CIE coordinates of (0.150, 0.054) and high color purity of 92.0%. These results demonstrate that this novel type of blue broadband Ca8(Al12O24)(WO4)2: Eu2+ phosphor has great potential in the field of optical applications under excitation of near-ultraviolet light.