Tunable emission color of Li2SrSiO4:Tb3+ due to cross‐relaxation process and optical thermometry investigation

A series of Li₂SrSiO₄:xTb³⁺ (0.2%, 0.4%, 0.6%, 0.8%, 2%, 4%, and 6%) phosphors were prepared by conventional solid‐state reaction. It was found that this silicate phosphor has a wide excitation band at near‐ultraviolet region (230‐300 nm) due to spin‐allowed 4f ⁸→4f⁷5d¹ transitions of Tb³⁺ ions, with the exact position dependent on the crystal field of the lattice. The cross‐relaxation process originating from ⁵D₃→⁵D₄ and ⁷F₆→⁷F₀ happened between different Tb³⁺ ions. It leads to the luminescence color of Li₂SrSiO₄: xTb³⁺ tuning from blue to green just by controlling Tb³⁺ concentrations. Furthermore, concentration quenching mechanism, energy migration type, cross‐relaxation rate and efficiency, are discussed in detail. Finally, optical thermometry properties were investigated via temperature‐dependent emission spectra. The results show that low‐concentration‐doped sample (Li₂SrSiO₄:0.4%Tb³⁺) shows remarkable optical thermometry based on fluorescence intensity ratio (FIR) between the blue and green emission of Tb³⁺ ions, whereas the high‐concentration‐doped sample (Li₂SrSiO₄:4%Tb³⁺) demonstrates small emission intensity loss. It illustrates that terbium‐doped silicate phosphor is a multifunctional material with potential application for display field and optical thermometry .