LiMgPO4:Tb,B - A new sensitive OSL phosphor for dosimetry

Optically Stimulated Luminescence (OSL) technique has emerged as a serious competitor to Thermally Stimulated Luminescence (TSL) technique in various dosimetric applications, especially after the development of crystalline alumina (Al₂O₃:C) doped with carbon. Since then, several attempts are being made to develop other possible materials for OSL based dosimetric applications. Efforts conducted in our laboratory in this direction have led to the development of a new phosphor, Lithium Magnesium Phosphate doped with terbium and boron (LiMgPO₄:Tb,B). This phosphor is prepared by solid-state diffusion method involving conventional air furnaces with operating temperature 1000 °C and easily amenable to large scale production without compromising primary dosimetric advantages. In this work we present some of the dosimetric OSL characteristics of this phosphor. The phosphor exhibits a main TSL peak at 250 °C. The phosphor also emits OSL, when the irradiated phosphor is stimulated with 470 nm light with the OSL sensitivity 1.3 times that of commercially available Al₂O₃:C. Photoluminescence (PL) emission spectrum consists of sharp lines characteristics of Tb³⁺ emission. The OSL discs made out of this phosphor are reusable up to at least 50 cycles, the phosphor exhibits dose linearity up to 1 kGy. Minimum detectable dose is found to be 20 μGy and fading of the OSL signal is found to be about 16% in four days, after which the OSL signal stabilizes.