Synthesis and Optical Properties of Eu²⁺ and Eu³⁺ Doped SrBP Phosphors Prepared by Using a Co-precipitation Method for White Light-Emitting Devices

Abstract

The Eu³⁺ and Eu²⁺-doped SrBP phosphor powders were synthesized via the co-precipitation method and subsequent reduction of the dopants in N₂/H₂ gas for application in white light-emitting devices (WLED). The as-prepared powders were annealed at a temperature range of 600°C to 1300°C in air ambient to form Eu³⁺-doped phosphors with an average particle size in the range of 100 nm to 1 μm. The phosphors were then reduced in the forming gas (90%N₂:10%H₂) to achieve Eu²⁺-doped phosphors. It has been found that typical phases of Sr₆P₅BO₂₀, Sr₂P₂O₇, and Sr₃(PO₄)₂ co-exist in the as-prepared powders. The strong and narrow orange-red emission from 570 nm to 700 nm in the photoluminescence spectra (PL) of the SrBP:Eu³⁺ phosphors are attributed to the ⁵D₀ → ⁷F_j transitions of Eu³⁺ ion (where j gets the value of 1 to 6). In contrast, the broad luminescence band of the SrBP:Eu²⁺ phosphors in the range of 400 nm to 500 nm are attributed to the 5d–4f transitions of Eu²⁺ ion in the same host crystal. The Eu³⁺/Eu²⁺-doped SrBP phosphors are considered to be promising phosphors for WLED. The co-precipitation method is simple and rapid, but allows for the controlling of particle size and composition with ease.