Tunable emission and concentration quenching of Tb3+ in magnesium phosphate lithium

Tunable photoluminescence of Tb3+-doped LiMgPO4 (Tb3+:LiMgPO4) phosphors with different Tb3+ concentrations are successfully synthesized by a high temperature solid-state reaction routine. X-ray diffraction (XRD) and photoluminescent spectroscope (PLS) are employed to characterize the phosphors. It is found that a suitable firing temperature is important for the synthesis of the phosphors, and pure phase material can only be obtained around 900 °C. PL spectra reveals typical 5D4 to 7Fj energy transition of Tb3+ ions, and the emission colors varied from red to green with Tb3+ concentration increasing, which is caused by the concentration quenching of Tb3+ emission centers in the LiMgPO4 matrix. The emissions peaking at 591, 619 and 695 nm are quenched at concentration of 1.5%, while the emissions at 489 nm and 543 nm are quenched at concentration of 8%. Further analysis of the data reveals two different energy transfer mechanisms for the five emission bands. The dipole-dipole model is proposed for the energy transfer of the red bands peaking at 694 nm, 619 nm and 591 nm, while the exchange interaction model is suggested for that of the green bands (543 nm and 489 nm), due to the different ion separations caused by different Tb concentrations.