Undoped and calcium doped borate glass system for thermoluminescent dosimeter

Abstract

Borate glasses present an absorption coefficient very close to that of human tissue. This fact makes some borates ideal materials to develop medical and environmental dosimeters. Glass compositions with calcium tetraborate (CaB4O7) and calcium metaborate (CaB2O4), such as the xCaB4O7−(100−x)CaB2O4 system (0⩽x⩽100wt%) were obtained by the traditional melting/quenching method. A phenomenon widely known as the ‘boron anomaly’ was observed in our thermal analysis measurements, as indicated by the increase of Tg and the appearance of a maximum value in the composition with 40wt% of CaB2O4. The Dy doped and Li co-doped 80CaB4O7–20CaB2O4 (wt%) glass samples were studied by the thermoluminescence technique. The addition of Dy improved the signal sensitivity in about three times with respect to the undoped glass sample. The addition of Li as a co-dopant in this glass caused a shift to a lower temperature of about 20°C in the main glow peak. The structural analysis of the 80CaB4O7–20CaB2O4 (wt%) undoped and doped samples were studied through infrared absorption. We have noted an increase in the coordination number of the boron atoms from 3 to 4, i.e., the conversion of the BO3 triangular structural units into BO4 tetrahedra.