Effect of method of preparation on the thermoluminescence and related defect centers in BaSO4:Eu,P phosphor

Recently, we have developed a sensitive BaSO4:Eu,P thermoluminescence (TL) phosphor which could be used as an x-ray storage phosphor and also for radiation dosimetry, personnel and environmental monitoring. In the present study, comparison is made between BaSO4:Eu,P phosphor prepared by three different methods viz., coprecipitation, sintering and recrystallisation. These phosphors were found to show different TL characteristics. The BaSO4:Eu,P phosphor prepared by re-crystallisation shows a very prominent TL peak at about 170 degC, whereas the phosphor prepared by the method of coprecipitation shows a main glow peak at 215 degC with small shoulder peaks at 170 degC and 270 degC respectively. The phosphor prepared by sintering shows a very broad peak centered at about 245 degC. Defect centres responsible for TL process were also investigated using the technique of electron spin resonance (ESR). In BaSO4:Eu,P phosphor, prepared by coprecipitation method, two distinct defect centres SO2-(A) and SO2-(B) assigned to SO2- radical, have been observed which could be correlated to the TL peaks at 170 degC and 215 degC respectively. No defect centre corresponding to 270 degC peak could be observed. In BaSO4:Eu,P prepared by sintering, same two defect centres were observed but no defect centre could be assigned to the 245 degC peak. Whereas in case of the phosphor prepared by the re-crystallisation method, only a single defect centre SO2-(A) was observed which could be correlated to the TL peak at 170 degC. An enhanced TL efficiency was also observed in BaSO4:Eu,P phosphor prepared by coprecipitation. (author)