Radiation Measurements 43 (2008) 375 – 378 www.elsevier.com/locate/radmeas Relative yields of radioluminescence and thermoluminescence in manganese- and silver-doped lithium tetraborate phosphors A. Kelemen a , ∗ , V. Holovey b , M. Ignatovych c a Institute of Isotopes, Hungarian Academy of Sciences, Department of Radiation Safety, P.O. Box 77, Budapest H-1525, Hungary b Institute of Electron Physics, National Academy of Sciences of Ukraine, 21 University Street, Uzhgorod 88000, Ukraine c Institute of Surface Chemistry, National Academy of Sciences of Ukraine, 17 Gen. Naumov str., Kyiv 03164, Ukraine Abstract Efficiency of energy storage is one of the most important questions in the investigation and the characterization of the thermoluminescent (TL) materials. The selection of the activator, its concentration, the structure of the host material will all influence the TL properties. The present paper reports on relative efficiency measurements of charge trapping in newly synthesized lithium-tetraborate based phosphors (Li 2 B 4 O 7 :Mn, Li 2 B 4 O 7 :Ag) based on subsequent measurements of radioluminescence and thermoluminescence in a specially designed TL reader. © 2008 Published by Elsevier Ltd. Keywords: Charge trapping; Radioluminescence; Thermoluminescence; Lithium-tetraborate 1. Introduction Over the past few decades there have been a continuously growing interest in radiation dosimetry, especially in the fields of environmental, personal and clinical applications. Although many materials are used as thermoluminescent (TL) phosphors in these fields today, a lot of efforts are in progress in order to develop new TL materials having better performance. Among the numerous characteristic features of a TL dosimeter, the tis- sue equivalence is one of the most important in the personal and clinical dosimetry. With the effective atomic number Z eff = 7.4, giving an extremely good energy response compared with hu- man tissue, metal or rare-earth ion impurities activated Li 2 B 4 O 7 (lithium-tetraborate, LTB) is widely used but at the same time a very promising material. Prokic (2002) showed that doped LTB phosphors have outstanding radiation stability with linear dose dependence in a very wide dose range (10 -3 .10 3 Gy). In addition the variation of the isotopic composition of the host material makes possible the separate detection of neutron and gamma doses. These are the reasons why doped LTB is a sub- ject of investigations nowadays (Can et al., 2006; Ishii et al., 2004; Miljanic et al., 2002, 2003). ∗ Corresponding author. E-mail address: kelemen@iki.kfki.hu (A. Kelemen). 1350-4487/$ - see front matter © 2008 Published by Elsevier Ltd. doi:10.1016/j.radmeas.2007.11.083 In recent years we are engaged in a systematic investiga- tion of LTB phosphors doped with transition or rare-earth ions (Ignatovych et al., 2005, 2007; Kelemen et al., 2007). Our work was devoted mainly to the spectroscopic characterization (opti- cal absorption, photoluminescence, PL and ESR) of the newly synthesized materials. The main goal of this series of measure- ments was to clarify the charge state of the dopants in different structures (crystalline and glassy) of the host and their role in the luminescent properties. We also studied the effect of radi- ation on changing of the ionization state of the dopants and its role in the TL properties. Now we pay attention to the TL efficiency of these materials. This feature of a material is determined by three factors: (1) the efficiency of charge trapping; (2) the probability of radiative recombination and (3) the amount of energy dissipated through non-radiative processes. It is well known, that TL materials show luminescence emission during the irradiation, it is called radioluminescence (RL). Its intensity is also determined by the three factors mentioned above. Let us denote N as the total number of free charge carriers cre- ated in the sample during the irradiation. A fraction of them n T will be trapped while the others will recombine. Let n R and n NR be the number of charge carriers going through radiative and non-radiative recombinations, respectively. N = n T + n R + n NR , and we may call Q = n T /N the trapping efficiency. During the