TL and PL studies on CaSO4CaSO4: Dy nanoparticles

Nanocrystalline CaSO4CaSO4: Dy of grain size 30 nm has been prepared by the chemical co-precipitation method and its photoluminescence (PL) and thermoluminescence (TL) characteristics have been studied. The PL emission spectrum of the nanophosphor resembles with that of the microcrystalline phosphor. Both the spectra show the two well-known bands at 482 and 573 nm. However, a shift towards lower wavelength of the excitation peaks has been observed on decreasing the particle size from micrometer to nanometer. This has been attributed to the extension in the band gap of Dy3+Dy3+ ions. The glow curve of the nanocrystalline materials has four major peaks at around 411, 498, 569 and 652 K. The TL intensity of the nanophosphor has been found to be less than that of its corresponding microcrystalline phosphor. Various peaks have been identified and separated using glow curve deconvolution (GCD) method. Trapping parameters for various peaks have been tabulated for the nanocrystalline materials and compared with those of the microcrystalline materials. It has been found that, there is change in the order of kinetics, while going from micro- to nanocrystalline powder. The TL intensity saturates at high doses in case of microcrystalline phosphor, while it becomes supralinear in case of nanocrystalline materials. This property along with negligible fading makes the nanocrystalline phosphor useful for its application to estimate high exposures of γγ-ray.