Study on the luminescence properties and energy transfer of Na4CaSi3O9:Ce3+, Sm3+ phosphor

In this work, we synthesize successfully Na4CaSi3O9:R (R = Ce3+, Sm3+, and Ce3+/Sm3+) phosphors in the reducing atmosphere (95% N-2 + 5% H-2) by using the high-temperature solid-state method. The crystal structure and luminescence properties of samples are investigated. The excitation spectrum of Na4CaSi3O9:Ce3+ phosphor is observed in the range of 220-400 nm due to the 4f -> 5d transitions of Ce3+ ion. The emission spectrum contered at similar to 425 nm of Na4CaSi3O9:Ce3+ phosphor is in the range of 360-650 nm owing to the 5d -> F-2(5)/(2) and F-2(7/2) transitions of Ce3+ ion. Na4CaSi3O9:Sm3+ phosphor can show the excitation spectrum in the range of 200-550 nm owing to the O2- - Sm3+ charge transfer band and the f - f transitions of Sm3+ ion, and its emission spectrum covers the region from 575 nm to 750 nm with four emission bands because of the (4)G(5/2) -> H-6(5/2), H-6(7/2), H-6(9/2), and H-6(11/2) transitions of Sm3+ ion. The tunable emission, luminescence improvement, temperature-dependent emission, and lifetime in Na4Ca0.96-xSi3O9:4 mol%Ce3+, xSm(3+) phosphors are investigated. The luminous mechanism of Na4CaSi3O9:Ce3+, Sm3+ phosphors is explained by using the energy level diagrams of Ce3+ and Sm3+ ions. The experimental results are beneficial to research new Ce3+ and Sm3+ co-doped phosphors.