Novel green emitting Tb3+ doped KCaF3 phosphor for WLEDs and TLD applications

Multifunctional green emitting (Potassium Calcium Fluoride: x Trivalent Terbium) KCaF₃: xTb³⁺ (x = 0.01, 0.03, 0.05, 0.07, 0.09, and 0.11 mol%) phosphor was synthesized by solid state reaction method. Crystal structure, morphology, photoluminescence and thermoluminescence properties were investigated in detail. Photoluminescence emission spectrum showed the characteristic maximum intensity peak at 543 nm corresponding to Tb³⁺ emission band when excited using an UV light of wavelength 374 nm. The concentration quenching effect of Tb³⁺ in KCaF₃ phosphor was caused by dipole – quadrupole interaction between Tb³⁺ ions. CIE coordinates of KCaF₃: xTb³⁺ (x = 0.05 mol%) was found to be x = 0.2959 and y = 0.6592 positioning at green region. Beta irradiated thermoluminescence glow curve was recorded on KCaF₃: xTb³⁺ (x = 0.05 mol%) phosphor. Low temperature signals in TL glow curve were removed using bleaching or preheating technique. The optimization of preheat temperature was performed using different temperature and found 125 °C (peak 1) and 210 °C (peak 2) as an optimized temperature. Temperature of maximum TL intensity (T_m) of peak 1 and peak 2 was found to be 181 °C and 292 °C, respectively. The activation energy (E_a) and frequency factor (s) of peak 1 and peak 2 were calculated using peak shape method and variable heating rate method (VHR). Characteristic studies for dosimetry application such as dose response and reusability of KCaF₃: xTb³⁺ (x = 0.05 mol%) were investigated in detail.