Synthesis and thermoluminescence study of Dy³⁺ doped NaCaPO₄ phosphor

Highly sensitive NaCaPO₄:Dy³⁺ micro-phosphor was successfully synthesized by a simple combustion method. The phosphor was doped with varying concentrations of Dy³⁺ ions (0.0-1.0 M%). After synthesis, the phosphor was crushed and sieved to obtain different particle sizes, and were given heat-treatments in the temperature range of 400-1200 °C for 3.0 h. The samples were characterized using X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), Electron Dispersive Spectroscopy (EDS) and Photoluminescence (PL) techniques. The XRD analysis confirmed that the newly prepared phosphor crystallized in an orthorhombic structure, belonging to the Pn21a (33) space group and matched well with the standard pattern from the JCPDS card number 76-1456. The NaCaPO₄:Dy³⁺ phosphor with impurity concentration 0.4 M%, particle size range 106-125 μm and annealed at 1200 °C exhibited the maximum TL sensitivity and was used for further study. The TL glow curve of the phosphor exhibited two prominent peaks at around 113 °C and 202 °C. Comparison of the sensitivity with commercially available TLD-700H and TLD-900 phosphors showed that the newly developed NaCaPO₄:Dy³⁺ phosphor was ∼3.0 times less sensitive than TLD-700H but about ∼6.0 times more sensitive than TLD-900. It also exhibited a linear and wide dose response in the range of 1.0 Gy-500 Gy. Activation energies and frequency factors determined using Various Heating Rate (VHR) and Computerized Glow Curve Deconvolution (CGCD) methods were found to be in good agreement. High sensitivity, simple synthesis, wide and linear dose response and excellent reusability make NaCaPO₄:Dy³⁺ phosphor a good candidate for TL dosimetry applications.