Hydrothermal synthesis of NaLa(WO4)2:Eu3+ octahedrons and tunable luminescence by changing Eu3+ concentration and excitation wavelength

NaLa(WO 4 ) 2 :Eu 3+ phosphors with different Eu 3+ concentrations have been synthesized by a hydrothermal method. The phase is confirmed by XRD analysis, which shows a pure-phase NaLa(WO 4 ) 2 XRD pattern for all of NaLa(WO 4 ) 2 :Eu 3+ phosphors. The SEM and TEM images indicate that all of NaLa(WO 4 ) 2 :Eu 3+ phosphors have a octahedral morphology. These suggest that the Eu 3+ doping has no influence on the structure and growth of NaLa(WO 4 ) 4 particles. By monitoring the emission of Eu 3+ at 615 nm, NaLa(WO 4 ) 2 :Eu 3+ phosphors show excitation bands originating from both host and Eu 3+ ions. Under the excitation at 271 nm corresponding to WO 4 2− groups, emission bands coming from the 1 A 1 → 3 T 1 transition with the WO 4 2− groups and the 5 D 0 → 7 F j (j = 0, 1, 2, 3 and 4) transitions of Eu 3+ are observed. The emission intensity relating to WO 4 2− groups decreases with increasing Eu 3+ concentration. But emission intensities of Eu 3+ increase firstly and then decreases because of concentration quenching effect. Under the excitation at 395 nm corresponding to 7 F 0 → 5 L 6 transition of Eu 3+ , only characteristic Eu 3+ emission bands can be observed. The results of this work suggest that tunable luminescence can be obtained for Eu 3+ doped NaLa(WO 4 ) 2 phosphors by changing Eu 3+ concentration and excitation wavelength.