Effect of phase transition and particle size on thermoluminescence characteristics of nanocrystalline K2Ca2(SO4)3:Cu+ phosphor

A new K2Ca2(SO4)3:Cu+ nanocrystalline TLD phosphor was prepared by chemical coprecipitation method using calcium chloride, potassium chloride and ammonium sulphate as reactants and copper chloride (Cu2Cl2, as impurity) in the presence of ethanol. The samples were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), Differential thermal and thermogravimetric analysis (DT-TGA) techniques. XRD and DTA data show that there is a phase transformation from orthorhombic to cubic occurring at around 550 K. The effects of impurity concentration, annealing temperature and γ rays dose on TL characteristics of the material have been studied. Different glow curves have been theoretically deconvoluted using computerized glow curve deconvolution (CGCD method) into simple glow peaks to determine their trapping parameters. The results show that different phases existing in the material on annealing might have reorganized the electron-traps (energy levels) and hole-traps (luminescence centers) and are responsible for changing glow curve structures. This is very important to know as any change in the glow curve structure would cause errors in estimation of doses of high-energy radiations and also may lose its reusability. The photoluminescence (PL) studies show that there are no redox reactions (Cu+ Cu2+) taking place and Cu remains in its Cu+ form after annealing and even after irradiation.

► Cost effective synthesis of new K2Ca2(SO4)3:Cu+ nanocrystalline TLD phosphor. ► Material characterizations by XRD, TEM and DT-TGA techniques. ► Changes in glow curve structures and trapping parameters on phase transitions. ► Estimation of high doses (∼kGy range) where microcrystalline TLDs saturate. ► Importance of the study for dose estimations and reusability of the material.