Investigation of the thermal quenching of two emission centers in Sr9MnLi(PO4)7:Eu2+ using time-resolved technique

Abstract

The thermal stability of the phosphors in phosphor-converted light-emitting diodes (LEDs) plays an important role in the practical application of lighting. Herein, the Mn²⁺-based red-emitting phosphors of pure and Eu²⁺-doped Sr₉MnLi(PO₄)₇ (SMPO) samples were prepared using the high temperature solid-state reaction method. The crystal field environment around the Mn²⁺ ions was analyzed by combining the results of photoluminescence excitation spectroscopy and Tanabe–Sugano diagrams. By comparing the results of X-ray photoelectron spectroscopy, two additional bands centered at about 129.8 eV and 130.7 eV were found in the Eu²⁺-doped sample, which corresponded to the chemical states of P 2p_3/2 and P 2p_1/2. Two different sets of emission spectra were observed for Sr₉MnLi(PO₄)₇:5%Eu²⁺ (SMPO:Eu²⁺) on employing the time-resolved technique. The emission peaks centered at 615 nm and 661 nm were attributed to Mn²⁺ and Eu²⁺ ions, respectively. The thermal quenching behaviors of Eu²⁺ and Mn²⁺ were investigated in the temperature range of 300–620 K and the thermal quenching mechanisms are given in this work. Systematic research on the luminescent properties of Eu²⁺ and Mn²⁺ ions in the SMPO:Eu²⁺ phosphor contributes to the understanding of the thermal stability and aids in the development of Mn²⁺-based red-emitting phosphors.