CaSO4Dy

CaSO4Dy, short for dysprosium-doped calcium sulfate, denotes a thermoluminescent phosphor prepared by introducing dysprosium ions into a calcium sulfate host lattice. The material absorbs energy from ionizing radiation and stores it at trap centers created by the Dy3+ dopants. When subsequently heated, the stored energy is released as visible light, with the emission largely arising from dysprosium transitions, including blue and yellow bands around 480 nm and 575 nm.

The compound is typically produced by converting calcium sulfate dihydrate (gypsum) to its anhydrous form and incorporating dysprosium at controlled concentrations. It is widely processed into powders, granules, or transparent pellets suitable for incorporation into thermoluminescent dosimeters (TLDs). The dose response and glow-curve shape depend on the Dy concentration, crystal form, and readout conditions.

CaSO4:Dy is valued in radiation dosimetry for its high sensitivity to ionizing photons and beta radiation, relatively simple fabrication, and reusability after annealing. It has been used in personal dosimeters, medical and industrial dosimetry, and radiography where thermoluminescent readout provides dose information without continuous electronics.

Limitations include the need for controlled annealing to erase previous doses and specialized thermoluminescence readers, as well as potential fading at room temperature over extended periods, depending on the specific preparation. Research continues to optimize doping levels and crystal quality to improve linearity, stability, and emission efficiency.