Synthesis and photoluminescence properties of Eu2+/Eu3+ or Ce3+/Eu3+ co-doped Sr5(BO3)3F compounds

The synthesis and photo-luminescence properties of Eu²⁺/Eu³⁺ or Ce³⁺/Eu³⁺ co-doped Sr₅(BO₃)₃F compounds are reported. Using the Sr₅(BO₃)₃F as the host, through the solid state reaction under the reductive atmosphere, Eu²⁺/Eu³⁺ and Ce³⁺/Eu³⁺co-doped samples were prepared. These compounds exhibit good photo-luminescence properties. Under the excitation of 376 nm, an unusual red orange emission coming from the Eu²⁺ ions can be obtained in Eu ions doped Sr₅(BO₃)₃F, which exhibits a broadband emission in the range of 450–800 nm with the peak at around 600 nm. At the same time, the characteristic f-f excitation and emission of Eu³⁺ can improve and adjust the Eu²⁺ emission in Eu³⁺/Eu²⁺ codoped Sr₅(BO₃)₃F. In addition, the adjustable luminescence properties from blue to white of Sr₅(BO₃)₃F:Ce³⁺, Eu³⁺ are investigated. The energy transfer behavior from Ce³⁺ to Eu³⁺ was confirmed. In the spectra of the co-doped samples, we can hardly observe the characteristic peak of Eu²⁺, because Ce⁴⁺ can oxidize Eu²⁺ to Eu³⁺, and Ce⁴⁺ itself is reduced to Ce³⁺. The CIE coordinates from (0.2758, 0.2420) to (0.3857, 0.3015) show Sr₅(BO₃)₃F:3%Ce³⁺, x%Eu³⁺ (x = 1,3,5,7,9) are in the white light emission region. All results demonstrate that the Sr₅(BO₃)₃F:Eu³⁺/Eu²⁺ and Sr₅(BO₃)₃F:Ce³⁺/Eu³⁺ phosphors have good application prospects for LED plant growth and white LED, respectively. The bond energy method was used to explain the reason why the Eu²⁺/Eu³⁺ ion instead of only Eu²⁺ and Ce³⁺/Eu³⁺ instead of Ce³⁺/Eu³⁺/Eu²⁺ can exist in the host Sr₅(BO₃)₃F. The theoretical analysis agree well with the experimental result.