Confirmation studies of correlation between TL and ESR of natural calcium fluoride

429-431Thermoluminescence (TL) and electron spin resonance (ESR) studies were carried out on natural calcium fluoride (Chougaonkar M P & Gundu Rao T K, Proc NCLA-2005, 2005). It was speculated from the studies that the first two TL peaks appearing approximately at 115 and 200oC may be related to two distinct O2-(I) and O2-(II) radicals, respectively. To assess the validity of the correlation between two ESR centres and the TL peaks, CaF2 without oxygen impurities were obtained by growing single crystals of natural CaF2 in oxygen free atmosphere. The oxygen contents in the host material were also removed using PbF2 as scavenger during the growth. ESR spectrum and TL glow curves were then recorded to study the effect of removal of oxygen from the lattice. The studies indicate that the addition of PbF2 leads to the removal of precursors of O2- radicals as well as CaO present in the lattice and yields clear transparent crystals. It has also been observed that the glow peaks appearing at 115 and 200oC were drastically reduced indicating the near absence of centres responsible for the TL peaks. ESR studies shows the absence radicals O2- I as well as O2- II, thus confirming that these centres are responsible for the TL peaks