Spectral study on energy transfer of the LiMgPO4 phosphor doped with Tm3+ and Tb3+

Abstract

LiMgPO4(LMP):Tm, LMP:Tb and LMP:Tm, Tb phosphors were synthesized via a high-temperature solid-phase method, and the crystal structures of the samples were studied by X-ray diffraction (XRD). Thermoluminescence (TL) and optically stimulated luminescence (OSL) curves and TL three-dimensional (3D) spectra of the LMP phosphors doped with Tm3+ and Tb3+ were measured. The photoluminescence (PL) of the samples was also measured to study the effects of Tb3+ and Tm3+ ions on the luminescence of the material, its concentration on the luminescence properties, and the energy transfer between the two kinds of ions. The experimental results showed that in the co-doped system of LMP:Tm,Tb, the rare earth ions, Tm3+ and Tb3+, become the discrete luminescent centre, Tm3+ ions act as activators, and Tb3+ ions act as sensitizers. Upon analysing the PL lifetime of Tm3+ and Tb3+, energy transfer from Tb3+ to Tm3+ was found. According to the TL 3D spectra of LMP:Tm,Tb, the TL luminescence of Tb3+ below 200 °C was suppressed, and the TL luminescence of Tm3+ at approximately 300 °C was enhanced. This showed that the energy of the low-temperature glow peaks transferred to the 300 °C peak, meaning that the formation of shallow traps was inhibited, which is beneficial for the stability of the sample signal and improves the sensitivity of the sample to the high-temperature peak. Moreover, the TL and OSL intensities of the LMP:Tm, Tb phosphor were comparable to that of Al2O3:C; thus, it can be applied for a low-dose measurement.