## 1 Introduction  
Fast progress and rising interest in technologies involving interactions of ionizing radiation with matter force the continuous development of dosimetric techniques. The number of dosimetric systems present nowadays on the market is limited, especially in the narrow field of high-dose radiation dosimetry (especially in dose ranges up to 35 KGy). Many of these systems are based on organic compounds and polymers (alanine, poly-methylmethacrylate, etc.) and have numerous limitations in terms of use in harsh environments. One of the potential alternatives that may turn out to be complementary to existing systems is phosphate glasses doped with terbium ions. Terbium is a lanthanide, belonging to the rare-earth elements (REE) group. REE include lanthanum and the f-block elements, cerium through lutetium. Next to the above, scandium and yttrium are included in this group as well, due to the similar ionic radii with the lighter f-block elements. Moreover, they co-exist together in the same types of ores [1]. Lanthanides exhibit an important feature, namely, they can play the role of light-emitting activators in various matrices. The rare earth phosphorus can be divided into two groups: the broad-band-emitting, owing to the 5d\(\rightarrow\)4f transition (Eu\({}^{2+}\), Ce\({}^{3+}\)), and the narrow-band-emitting, owing to the transition between the 4f levels like Tb\({}^{3+}\). Terbium ion emits green light due to the four sharp peaks arising from \({}^{5}\)D\({}_{4}\)\(\rightarrow\)\({}^{7}\)F\({}_{\text{j}}\) transitions, where J = 3, 4, or 6,with the strongest emission peak at 550 nm [2; 3]. Terbium possesses only one stable isotope Tb-159, characterized by a low nuclear spin value (I = 3/2), and exhibits a relatively simple hyperfine structure of its electronic levels [4]. Terbium ions (Tb\({}^{3+}\)) are very often used as dopants in order to extend luminescence properties in various materials, e.g., in nitridosilates, glasses, and ceramics [5; 6; 7; 8]. Terbium ions are also able to play the role of activators in mechano-luminescence light-emission processes, often as inorganic salts such as sulphates, carbonates, nitrates, and chlorides [9; 10]. Terbium dopants have been also used in various types of thermoluminescent (TL) materials. For example, magnesium orthosilicate doped with terbium (Mg\({}_{2}\)SiO\({}_{4}\):Tb) has been investigated in TL dosimetry since 1971, thanks to its high sensitivity and effective atomic number of 11 [11; 12]. Unfortunately, TL properties of orthosilicates might be unstable, which are strongly influenced by the preparation method [13]. Another group of light-emitting materials that are based on terbium dopant, improving their TL properties, are ionic crystals, e.g., CsCl:Tb\({}^{3+}\), terbium-doped strontium pyrophosphates (Sr\({}_{2}\)P\({}_{2}\)O\({}_{7}\):Tb\({}^{3+}\)), potassium bromide crystals, and terbium-doped double fluorides [14; 15; 16; 17]. Moreover, the application of terbium oxide as a dopant significantly improved the properties of materials that had been already used in TL dosimetry. A straightforward example of such materials is aluminum oxide doped with terbium and thalium [18]. Lu\({}_{2}\)O\({}_{3}\):Tb,Ta ceramic storage phosphors are also a good example of how the presence of terbium ions can significantly change the thermoluminescence properties of materials; Tb,Ta ceramics show high overall TL intensity [19]. Despite all the advantages of the crystal-based phosphors, they possess drawbacks as well. For TL dosimeters based on crystalline systems, one can observe an increased light-scattering efficiency, due to their limited transparency. A reasonably good alternative for these phosphors might be found among dosimetric systems based on glasses, for example, borosilicate glasses [20]. One such example is zinc-lithium-borate glass doped with terbium. Introduction of terbium into the material results in an increase of TL yield, enhancement of sensitivity of the phosphor, and significant minimization of fading behavior [21].