A New High Sensitive CaSO4 : Dy Thermostimulated Luminescence Phosphor

This paper reports the development of a high sensitive CaSO4 : 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 CaSO4 : Dy (P). The TSL sensitivity of N (<75 μm) 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 104 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—4 and SO—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 Dy3+ lines in both samples but minor changes in their relative intensities between them were noticed. Since the new CaSO4 : Dy material has better basic TSL characteristics, the new preparation technique (N) is advantageous relative to the presently (P) used one.