<p>A series of novel broadband blue-emitting Ca<sub>8</sub>(Al<sub>12</sub>O<sub>24</sub>)(WO<sub>4</sub>)<sub>2</sub>: <i>x</i>% Eu<sup>2+</sup> (0.1≤<i>x</i>≤2.5) phosphors were synthesized via the solid-state method. The analysis of crystal structure and the X-ray diffraction confirms that the Ca<sub>8</sub>(Al<sub>12</sub>O<sub>24</sub>)(WO<sub>4</sub>)<sub>2</sub>: Eu<sup>2+</sup> phosphors are phase-pure and crystallize in the orthorhombic system with space group Aba2. The wide bandgap energy of the Ca<sub>8</sub>(Al<sub>12</sub>O<sub>24</sub>)(WO<sub>4</sub>)<sub>2</sub> host provides a suitable bandgap environment for Eu<sup>2+</sup> ions. Under 325 nm excitation, the Ca<sub>8</sub>(Al<sub>12</sub>O<sub>24</sub>)(WO<sub>4</sub>)<sub>2</sub>: Eu<sup>2+</sup> exhibits a broad blue-emitting band in the range of 380–550 nm, resulting from the 4f<sup>6</sup>5d<sup>1</sup>→4f<sup>7</sup> transition of Eu<sup>2+</sup>. As the concentration of Eu<sup>2+</sup> increases, the emission peak of Ca<sub>8</sub>(Al<sub>12</sub>O<sub>24</sub>)(WO<sub>4</sub>)<sub>2</sub>: Eu<sup>2+</sup> undergoes a redshift, originating from the site competition by Eu<sup>2+</sup> doping. Concurrently, due to concentration quenching, the emission intensity initially increases and subsequent decreases, reaching a maximum at an optimal Eu<sup>2+</sup> doping concentration of 0.3%. The concentration quenching mechanism was confirmed to be electric dipole-dipole interaction. Additionally, the optimally doped Ca<sub>8</sub>(Al<sub>12</sub>O<sub>24</sub>)(WO<sub>4</sub>)<sub>2</sub>: 0.3% Eu<sup>2+</sup> 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 Ca<sub>8</sub>(Al<sub>12</sub>O<sub>24</sub>)(WO<sub>4</sub>)<sub>2</sub>: Eu<sup>2+</sup> phosphor has great potential in the field of optical applications under excitation of near-ultraviolet light.</p>

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Multiple site occupancy induced a novel broadband Ca8(Al12O24)(WO4)2: Eu2+ blue phosphor for pc-WLEDs

  • Ningning Feng,
  • Jiangshan Han,
  • Hua Jiao,
  • Lin Yuan,
  • Guoqing Zhang,
  • Boyu Wang,
  • Kang Zhao

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.