Effect of Eu3+ Concentration on the BaAl2O4/CaAl4O7: x% Eu3+ (0 ≤ x ≤ 5.5) Mixed-Phase Nanophosphors Synthesized Using Citrate Sol-Gel Method

A series of undoped mixed‐phase BaAl 2 O 4 /CaAl 4 O 7 (hereafter called BC) and doped BC: x % Eu 3+ (0 < x ≤ 5.5) nanophosphors were successfully prepared by the citrate sol‐gel technique. Their structure, morphology, and optical properties were studied in detail by X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and photoluminescence (PL) spectroscopy. XRD and SEM showed that all the BC: x % Eu 3+ samples consisted of the crystalline structure of the mixed phases of both the BaAl 2 O 4 and CaAl 4 O 7 materials. The structure resembles more that of the BaAl 2 O 4 than the CaAl 4 O 7 phase. The TEM results suggest that the crystallite sizes are in the nanometer scale with rod‐like particles. PL results showed multiple emission peaks located at 436, 590, 616, 656, and 703 nm, which were assigned to the intrinsic defects within the BC matrix, 5 D 0 ⟶ 7 F 1 , 5 D0 ⟶ 7 F 2 , 5 D 0 ⟶ 7 F 3 , and 5 D 0 ⟶ 7 F 4 transitions of Eu 3+ , respectively. The decay curves evidently showed that the nanophosphors have persistent luminescence. The Commission Internationale de l’Eclairage (CIE) analysis revealed that doping has tuned the emission colour from blue to orange‐red. The results indicate that the Eu 3+ ‐doped samples can potentially be used in the orange/red‐emitting phosphors.