Role of Li + ions on the surface morphology and thermoluminescence properties of Y 2 O 3 :Tm 3+ nanophosphor.

Y ₂ O ₃ :Tm ³⁺ and Li ⁺ co-doped Y ₂ O ₃ :Tm ³⁺ nanopowders were synthesized using the solution combustion method for possible application in ultraviolet (UV) light dosimetry. X-ray diffraction revealed the crystallite sizes to be in the range 21-44 nm and 30-121 nm using the Scherrer equation and the W-H plot relationship, respectively. Field emission scanning electron microscopy confirmed that, after co-doping with 4 mol% concentration of Li ⁺ , the particles were spherical in nature with an average size of ~30 nm. Fourier transformed infrared spectroscopy results showed bands at wavenumbers of 556, 1499, 1704, 2342, 2358, 2973, 3433, and 3610 cm ^-1 that corresponded to the stretching and bending vibrations of Y-O, C=O and O-H. Thermoluminescence (TL) glow peaks for Y ₂ O ₃ :Tm ³⁺ nanophosphors observed at 399 and 590 K were attributed to oxygen defects caused using UV irradiation. These oxygen defects firstly resulted in an increased prominent peak TL intensity for up to 270 min of irradiation and then a decrease. This was attributed to the presence of oxygen defect clusters that caused a reduction in recombination centres. The Li ⁺ co-doped sample showed peaks at 356, 430, and 583 K and its intensity sublinearly increased up to 90 min and then thereafter decreased. The TL trapping parameters were calculated using computerized glow curve deconvolution methods. The Li ⁺ co-doped sample exhibited less fading and high trap density under the UV radiation.
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