Synthesis, thermoluminescence, defect center and dosimetric characteristics of LiF:Mg,Cu,P,Si phosphor

LiF:Mg,Cu,P,Si (MCPS), a new tissue equivalent phosphor, was synthesized by solid state method. Powder x-ray diffraction and scanning electron microscope were employed to determine the structural features. The dosimetric characteristics, electron spin resonance (ESR) and defect centers of this newly prepared phosphor were investigated. The MCPS phosphor is highly sensitive when compared with LiF:Mg,Ti and LiF:Mg,Cu,P (MCP), with the TL sensitivity being 35 times and 1.3 times higher respectively. The dosimetric peak occurs at 220 degrees C with a well defined glow curve structure similar to MCP. MCPS phosphor shows a linear dose response till 10 Gy. The minimum detectable dose has been found to be 8 Gy. The thermal stability of the phosphor could be enhanced by 20 degrees C from 240 degrees C to 260 degrees C when compared to MCP. Defect centers formed in the phosphor by gamma irradiation have been studied by ESR to identify the centers associated with the TL process in this phosphor. Thermal annealing experiments reveal the presence of several defect centers. Center I which shows an isotropic g factor of 2.0233 has been found to relate with the TL peaks at 160 degrees C, 220 degrees C and 265 degrees C. Centers II and III are characterized by isotropic g values of 2.0096 and 2.0019 respectively and are attributed to F centers.Board of Research in Nuclear Science, Department of Atomic EnergyCAPES, BrazilVelammal Engn Coll, Solid State Chem Res Lab, Dept Chem, Chennai 600066, Tamil Nadu, IndiaBhabha Atom Res Ctr, Radiol Phys & Advisory Div, Bombay 400085, Maharashtra, IndiaUniv Sao Paulo, Inst Phys, BR-05508090 Sao Paulo, SP, BrazilUniv Fed Sao Paulo, Dept Ciencias Mar, Rua Doutor Carvalho de Mendonca 144, BR-11070100 Santos, SP, BrazilUniv Fed Sao Paulo, Dept Ciencias Mar, Rua Doutor Carvalho de Mendonca 144, BR-11070100 Santos, SP, BrazilBoard of Research in Nuclear Science, Department of Atomic Energy: 2008/36/91-BRNS/2886Web of Scienc

Role of defect centres in thermoluminescence mechanism of Tb³⁺doped MgAl₂O₄

420-425Magnesium aluminate (MgAl2O4) doped with terbium was prepared by combustion synthesis. Defect centres of MgAl2O4:Tb are studied by correlating various techniques such as Electron Spin Resonance (ESR), Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL). TL studies on MgAl2O4:Tb3+ show two TL peaks at 120 and 340°C. MgAl2O4:Tb3+ exhibits OSL when stimulated with 470 nm blue light. ESR study shows two defect centres with g = 2.011 and g = 2.0052 which are assigned to V- centre and F+ centre, respectively. Step annealing ESR technique study suggests that V-centre is correlated to 120°C TL peak whereas F+ centre is correlated with both the 120 and 340°C TL peaks. A TL mechanism is proposed. ESR–OSL correlation studies are carried out. The results of ESR-OSL correlation study along with TL bleaching study support the proposed TL mechanism of 120°C TL peak