Abnormal thermal quenching behavior and optical properties of a novel apatite-type NaCa3Bi(PO4)3F:Sm3+ orange-red-emitting phosphor for w-LED applications

Novel apatite-type NaCa 3 Bi(PO 4 ) 3 F: x Sm 3+ (0.01 ≤  x  ≤ 0.30) orange-red-light phosphors were synthesized through the solid-state method at high temperature. The crystal structure, energy band structure , density of state, phase purity, particle morphology , photoluminescence properties, thermostability, and luminescence decay of the phosphors were comprehensively characterized. When λ ex  = 404 nm, the optimal NaCa 3 Bi(PO 4 ) 3 F:0.05 S m 3+ phosphor showed the orange-red emission (597 nm). The NaCa 3 Bi(PO 4 ) 3 F:Sm 3+ phosphors exhibited abnormal thermal quenching properties as their emission intensity increased by about 2.57% from 300 to 380 K. Their intensity at 440 K was still 1.01-fold stronger than that at room temperature. The abnormal thermal quenching mechanisms were well explained via the coordinate configuration scheme. The thermal activation energy ( E a ) was calculated to be 0.79 eV. The color purity of all the phosphors reached 99.9%. Ultimately, a white light-emitting diode (w-LED) was fabricated based on the tri-color RGB method. The color rendering index and the chromaticity coordinates of the fabricated w-LED were 89 and (0.310, 0.319), respectively. Thus, these high thermostability NaCa 3 Bi(PO 4 ) 3 F:Sm 3+ orange-red phosphors can be potentially used in w-LED applications.