Study of effect of mechanical deformation on thermoluminescence of gamma-ray-irradiated Dy doped MgSO4 phosphors

In order to find the mechanical stability of traps/luminescence centers responsible for TL in MgSO4:Dy system, effect of deformation on TL of MgSO4:Dy was studied. TL glow curve of MgSO4:Dy phosphor is complex and peaks around 110, 150 and 220 °C were observed. Optimum TL was obtained for the sample having 0.1 mol% concentration of Dy in MgSO4 system. Slight increase in intensity of 110 °C peak was observed when the TL glow curve was recorded after deforming the irradiated samples by dropping a piston of mass 0.4 kg onto it from the height of 0.2 m. Further increasing the height from which the piston was being dropped TL peak intensity of 110 °C decreased. However, 150 °C and 220 °C TL peak intensity decreased with deformation. Result showed that trap centers associated with 150 °C and nearby TL peaks were most mechanically unstable. TL spectrum of MgSO4:Dy phosphors was also recorded. Two peaks one at 490 nm and another at 590 nm were observed. In the TL emission spectra recorded for deformed samples, no significant change was seen in the peak positions. However, peak intensity was reduced. It is suggested that the recombination of electrons released from the traps during the thermal excitation is responsible for the TL emission in this system. It seems that in MgSO4:Dy system deformation does not cause any appreciable change in the recombination mechanism, it causes redistribution of traps and therefore change in relative TL intensity occurs in the same spectral region.