A New High Sensitive CaSO4 : Dy Thermostimulated Luminescence Phosphor

Abstract

This paper reports the development of a high sensitive CaSO 4 : Dy thermostimulated luminescence (TLD) phosphor prepared by a new (N) inexpensive technique. Scanning electron microscope photographs reveal that its crystal morphology is quite different from the presently used CaSO 4 : Dy (P). The TSL sensitivity of N (<75 mm) is nearly 60% higher than that of P at low dose levels. Below 1 Gy, the major TSL glow peak of N as well as P occurs at the same temperature ($230 C). The 130 C peak as well as the peaks in the region 300-350 C are very small in N when compared to those in P. While the glow curve shape of N is nearly invariant with radiation dose up to 10 4 Gy, P exhibits drastic glow curve changes at dose levels ! 10 Gy. As a result, the supralinearity of N above 10 Gy is considerably less than that of P. ESR signal in N due to the SO À 4 and SO À 3 radicals related to peak(s) around 130 C are less intense than those in P. Though the different X-ray diffraction lines of the two powder samples occur at the same d spacings, the relative intensities of almost all the minor lines are considerably reduced in N. The TSL and photoluminescent (PL) emission spectra show the characteristic 480 and 570 nm Dy 3+ lines in both samples but minor changes in their relative intensities between them were noticed. Since the new CaSO 4 : Dy material has better basic TSL characteristics, the new preparation technique (N) is advantageous relative to the presently (P) used one.

Synthesis and properties of submicron range CaSO4:Eu particles

“…Rare earth (RE)-doped CaSO 4 phosphors continue to receive attention of research workers [1,2]. As early as 1955, Sm-doped CaSO 4 was shown to have useful properties for applications in thermoluminescence dosimetry of iodizing radiations [3,4].…”

Influence of Li dopants on thermoluminescence spectra of CaSO4 doped with Dy or Tm

“…2) confirm the earlier data for rare earth doped calcium sulphates that emission spectra of CaSO 4 :Li, Dy or Tm are dominated by characteristic emission lines of Dy 3 þ or Tm 3 þ , as reported in other literature [4,8]. A possible process of TL in CaSO 4 (RE) phosphors was discussed by Lapraz et al [21].…”

“…These sulphates are widely used for both individual and environmental radiation monitoring [1][2][3]. Their popularity has led to an extensive series of studies aimed at elucidating their behavior, attempting to assess the underlying mechanisms, and efforts to predict, or empirically develop new variants of these phosphors [4][5][6][7][8][9][10]. One particularly interesting result was reported by Dr Prokic who found that the addition of a lithium co-dopant during preparation of the CaSO 4 :Dy (or Tm) results in a major increase of luminescence efficiency.…”

Thermoluminescent characteristics of LiF:Mg, Cu, P and CaSO4:Dy for low dose measurement

“…In other investigations [19], [22], [23] have been reported sensitivity factor values about 60% more than TLD-100 for CaSO 4 :Dy. The most sensitive is CaSO 4 :Dy and the second one is LiF:Mg,Cu,P.…”