Investigation of optical properties and thermoluminescence mechanisms of different ion doped lithium tetraborate phosphors

Thermoluminescence (TL) is the most common method used in radiation dosimetry. Differention-doped lithium tetraborate (Li2B4O7, LTB) materials are widely used as thermoluminescence dosimetry (TLD) due to the effective atomic number as tissue equivalent. Moreover, their use as optoelectronic materials is becoming increasingly widespread because of their interesting optical properties. In this thesis, the luminescence properties of Ag-doped, Cu-doped at two different concentrations, and Mn-doped at three different concentrations LTB materials such as Li2B4O7:Ag (0,25%), Li2B4O7:Cu (0,25%), Li2B4O7:Cu (0,62%), Li2B4O7:Mn (0,30%), Li2B4O7:Mn (0,68%) and Li2B4O7:Mn (0,53%) were investigated. In order to determine the dosimetric properties of the materials, the glow curve structures, dose-response curves and stability of the materials were investigated. Various heating rate method, Tmax-Tstop method and isothermal decay method are used to determine the trap parameters such as activation energy (E), frequency factor (s) and kinetic order (b) of the dosimetric materials used. In addition, emission spectra and crystal structure of these dosimetric materials were investigated by radioluminescence and optical absorption. In the radioluminescence spectra for the Ag doped material at 270 nm , for the 0,25% Cu doped sample at 350 nm, for the 0.62% Cu doped sample at 370 nm, at the different concentrations in the Mn doped material, about 430 nm and 610 nm bands were obtained. In the optical absorption spectrum, bands were observed at 205 nm for Ag ion and at about 360 nm for Cu ion. The increase in Cu concentration increases the absorption intensity. In the Mn-doped samples bands that peaked at about 360 and 600 nm corresponding to the excitation spectra of Mn2+ ions were observed.