Novel red and green emitting Li2SiN2:Eu3+/Tb3+ phosphors with a broad charge transfer band

Abstract

In this work, a broad excitation band of Li₂SiN₂:Eu³⁺ with the peak at 357 nm has been found and investigated. The photoluminescence, morphologies and thermal stability of the samples were also measured. Under excitation at 357 nm and 300 nm, sharp red and green light can be observed due to the ⁵D₀–⁷F₂ transition of the Eu³⁺ ions and the ⁵D₄–⁷F₅ transition of the Tb³⁺ ions, respectively. According to the Diffuse reflectance spectra in combination with the energy level diagram of Li₂SiN₂:0.02Eu³⁺, we deduced that the broad excitation bands belong to the charge transfer band (CTB), which have also been observed in Li₂SiN₂:Tb³⁺ with the peak at 271 nm. And the thermal stabilities of the samples have been found to be connected with the CTB.