X-ray absorption spectroscopy and X-ray photoelectron spectroscopy studies of CaSO_4:Dy thermoluminescent phosphors

摘要

Extended X-ray absorption fine structure (EXAFS) measurements have been carried out on CaSO_4:Dy phosphor samples at the Dy L_3 edge with synchrotron radiation. Measurements were carried out on a set of samples which were subjected to post-preparation annealing at different temperatures and for different cycles. The EXAFS data have been analysed to find the Dy-S and Dy-O bond lengths in the neighbourhood of the Dy atoms in a CaSO_4 matrix. The observations from EXAFS measurements were verified with XANES and XPS techniques. On the basis of these measurements, efforts were made to explain the loss of thermoluminescence sensitivity of CaSO_4:Dy phosphors after repeated cycles of annealing at 400℃ in air for 1 h.