Synthesis and TL characteristics of MgB4O7:Mn,Tb phosphor

Abstract

In the present paper optimized dosimetric characteristics of low-Z magnesium tetra-borate MgB4O7:Mn,Tb using a thermoluminescence (TL) technique have been reported. The phosphor material was synthesized using a conventional high temperature solid-state diffusion reaction. The crystalline structure and phase purity of synthesized powder were confirmed by powder X-ray diffraction (XRD) analysis. The material in the microcrystalline form was found to be in orthorhombic form. The comparative dosimetric properties of the phosphor material have been extensively investigated for its applications in personal and medical dosimetry. It has been found that the codoped MgB4O7:Mn,Tb material, exposed to γ rays, shows better TL sensitivity and has an edge over the Mn and Tb doped samples as it is much more sensitive than the formers (550 and 40 times, respectively, more than the later ones). It has a simple glow curve structure (two well separated TL peaks centered at around 475 and 650K). They are sufficiently above the room temperature (RT) to show low fading (~10% in a month after storing in dark at RT). However, the fading is much faster, if exposed to sunlight/room light/UV radiation. This has been a serious problem with many borate based phosphors. A detailed study on bleaching to UV–visible light of different wavelengths (energies) has been carried out and a new mechanism based on redox reactions is proposed. Low fading (~10% in a month) at room temperature on storing in dark, high TL sensitivity (3.5 times than that of TLD-100), tissue equivalence (Zeff≈8.23) and linear dose response up to wide range (0.1Gy to ~5.0kGy) of γ rays make it a suitable candidate for the radiation dosimetry and monitoring. However, it needs to be protected from sunlight/room light for fast fading.