Comparative studies on OSL properties of LiMgPO4:Tb,B powders and crystals

Abstract

The OSL properties of the LiMgPO4:Tb,B (LMP: Tb,B) were compared for samples in the form of powders and crystals. The LMP:Tb,B powders were synthesized by a solid state reaction with Tb and different kinds of boron donors. In turn, the LMP:Tb,B crystals were prepared by a micro-pulling down crystal growth method using the synthesized powder as a starting material. The automated Risø TL/OSL-DA 20 reader was utilized for the irradiations (90Sr/90Y source) and OSL measurements as well. The repeatability, dose response characteristic and fading were investigated for both types of samples. The LMP:Tb,B powders and crystals emit OSL, when previously irradiated samples are stimulated with blue light, with the OSL sensitivity comparable with a commercial Al2O3:C. The OSL signals of the LMP:Tb,B powders and crystals are repeatable (the standard deviation did not exceed 3.5%). The dose response for powders and crystals was found to be linear over the analyzed dose range, namely from 0.5 mGy up to 5 Gy.The fading was calculated considering, as the first measurement point, the OSL signal measured 24 h after the irradiation. This was measured with and without a pre-readout thermal treatment (60 s pre-heat in 150 °C). Such a procedure stabilizes the OSL signal for both types of samples. In case of powder samples, about 75–80% of the initial OSL signal was measured three weeks after the irradiation, if the pre-heat procedure was not applied. However, for crystal samples the level of OSL signal was about 15% higher. The pre-readout thermal treatment caused that the residual OSL signal for powders was about 80–90% and about 95% for crystals.