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

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.