A new phosphate phosphor K₅Y_1−xSm_x(P₂O₇)₂ with bright orange-red emission and good thermal stability

These days, there is a great demand for the development of orange-red phosphors for temporary applications in the sides of lighting and display. In this work, we synthesized a fresh type of orange-red phosphor with K₅Y(P₂O₇)₂-doped Sm³⁺ by high-temperature solid-state method, and used powder X-ray diffraction (XRD) method to study the crystal structure of prepared samples. Due to the 4f → 4f transition of Sm³⁺, when excited by near-UV light at 402 nm, K₅Y(P₂O₇)₂:Sm³⁺ phosphor emits orange-red light. The optimized Sm³⁺ concentration was found at 12%. Because of the concentration quenching, further increasing the Sm³⁺ concentration will reduce the intencity. The concentration quenching is originated from dipole–dipole interaction between Sm³⁺ ions. At 200 °C, the relative luminescence intensity is still about 70.3% of the intensity at 25 °C, meaning that K₅Y_0.88Sm_0.12(P₂O₇)₂ has good thermal stability. The chromaticity coordinates CIE were calculated to be (0.5813, 0.416), corresponding to orange-red color. All these results suggest that K₅Y_0.88Sm_0.12(P₂O₇)₂ is a promising orange-red phosphor.