White-light emitting BaAl2O4/CaAl4O7:x% Dy3+ (0 ≤ x ≤ 3) mixed phase nanophosphors synthesized using citrate sol-gel method

Abstract

Novel mixed phase BaAl2O4/CaAl4O7 (BC) and BC: x% Dy3+ (0 ≤ x ≤ 3) nanophosphors were synthesized by the citrate sol-gel method. The morphology changed as x%Dy3+ varied. The patterns showed that the BC nanophosphors matched well with the monoclinic CaAl4O7 and hexagonal BaAl2O4 structures. Moreover, the structure of BC was not influence by the dopant. The dopant is mainly located in the BaAl2O4 phase. The crystallite sizes were estimated to be in the nanoscale order. The photoluminescence (PL) results showed that the emission was quenched for BC: x% Dy3+ (x > 2.4) be due to the quadrupole-quadrupole interaction. The emission peaks at 325, 482 and (563 and 576) nm were assigned to the bandgap defects of BC, 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions of Dy3+, respectively. The International commission on illumination (CIE) showed the dopant (Dy3+) had changed the emission color from blue to white. This showed that the BC: x% Dy3+ (1.2 ≤ x ≤ 3) nanophosphors were potential candidates for white-light LEDs.