Photoluminescence and comparative thermoluminescence studies of UV/γ-irradiated Dy³⁺ doped bismuth silicate phosphor

Abstract

A series of Bi₄Si₃O₁₂:Dy³⁺ phosphor have been synthesized via conventional solid-state reaction method and its luminescence properties were investigated as near cool white light emitting and long afterglow phosphor. Crystal structure and phase structure characterization is determined using X-ray diffraction (XRD), SEM and EDS. Rietveld structural refinement and XRD confirms that prepared sample exhibit pure cubic structure [space group I-43d]. Photoluminescence spectra of both doped and undoped Bi₄Si₃O₁₂ phosphor were efficiently excited in the range of 200-450 nm, and prepared phosphor under 272 nm excitation exhibit three emission peaks located at 463 nm(blue), 482 nm(blue) and 576 nm (yellow) corresponding to ³P₁ → ¹S₀, ⁴F_9/2 → ⁶H_15/2 and ⁴F_9/2 → ⁶H_13/2 transitions. Characteristic emission peaks of Dy³⁺ centered at 482 nm and 576 nm were assigned for white light emission. The calculated Commission Internationale de I’Eclairage (CIE) chromaticity confirms that with Dy³⁺ doping, the luminescence co-ordinates of Bi₄Si₃O₁₂ phosphor shift to near white(x = 0.316, y = 0.358) region which is close to commercial pc-LED (Blue LED + YAG:Ce³⁺) (x = 0.320, y = 0.320) co-ordinates. Computation of correlated color temperature 6184 K endorses that prepared phosphor is cool in nature and can be served as white light emitting phosphor. Comparative thermoluminescence study of UV and γ-irradiated Bi₄Si₃O₁₂:Dy³⁺ phosphor is performed for the dosimetry application. TL intensity is recorded maximum at 30 min under UV irradiation (256 nm), and for γ irradiation, it was recorded at 10 kGy dose rate. γ-irradiated Bi₄Si₃O₁₂:Dy³⁺ phosphor TL study is reported for the first time at different dose rate and concentration for high dosimetry application. The defect characteristic is examined, Trap depths and other kinetic parameters are also evaluated by Chen’s peak shape method. Decay and fading measurement under UV/γ irradiation are performed to examine the long after glow properties of prepared samples. TL emission spectrum studies are also performed.