Sm3+ and Eu3+ codoped SrBi2B2O7: a red-emitting phosphor with improved thermal stability

Abstract

The thermal stability of luminescence is very critical for white light-emitting diodes. However, it is a continuous challenge to improve the thermal stability of red phosphors. In this study, Sm³⁺ and Eu³⁺ codoped SrBi₂B₂O₇ was synthesized by a high temperature solid state reaction method. It was found that the thermal stability of the synthesized phosphors was improved as Sm³⁺ was used as the sensitizer for Eu³⁺ doped into SrBi₂B₂O₇. Combined with a local crystal environment study and the first-principles calculations, the origin of the improvement of this thermal stability was studied in detail. The doped Sm³⁺ and Eu³⁺ ions were inclined to occupy Bi(1) (6c) and Bi(2) (6c) sites simultaneously and the crystal structure of the SrBi₂B₂O₇:Sm³⁺, Eu³⁺ was more compact at high temperature than that at room temperature. Thus, the defect formation energy was very low in the Sm³⁺ and Eu³⁺ codoped SrBi₂B₂O₇ phosphor, which is the main reason to improve the thermal stability with Sm³⁺ and Eu³⁺ codoped into SrBi₂B₂O₇. This study provides a new idea for developing a new method to improve the thermal stability of red-emitting phosphors.