ABSTRACT
A series of Ce3+ ion single-doped Ca2 Al2 SiO7 phosphors was synthesized by a combustion-assisted method at an initiating temperature of 600 °C. The samples were annealed at 1100 °C for 3 h and their X-ray diffraction patterns confirmed a tetragonal structure. The phase structure, particle size, surface morphology and elemental analysis were analyzed using X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy techniques. Thermoluminescence (TL) intensity increased with increase in ultraviolet (UV) light exposure time up to 15 min. With further increase in the UV irradiation time the TL intensity decreases. The increase in TL intensity indicates that trap concentration increased with UV exposure time. A broad peak at 121 °C suggested the existence of a trapping level. The peak of mechanoluminescence (ML) intensity versus time curve increased linearly with increasing impact velocity of the moving piston. Mechanoluminescence intensity increased with increase in UV irradiation time up to 15 min. Under UV-irradiation excitation, the TL and ML emission spectra of Ca2 Al2 SiO7 :Ce3+ phosphor showed the characteristic emission of Ce3+ peaking at 400 nm (UV-violet) and originating from the Ce3+ transitions of 5d-4f (2 F5/2 and 2 F7/2 ). The photoluminescence (PL) emission spectra for Ca2 Al2 SiO7 :Ce3+ were similar to the ML/TL emission spectra. The mechanism of ML excitation and the suitability of the Ca2 Al2 SiO7 :Ce3+ phosphor for radiation dosimetry are discussed. Copyright © 2016 John Wiley & Sons, Ltd.
Subject(s)
Aluminum/chemistry , Calcium/chemistry , Cerium/chemistry , Luminescent Measurements/methods , Oxygen/chemistry , Silicon/chemistry , Luminescence , Mechanical Phenomena , Phosphorus/chemistry , TemperatureABSTRACT
In this work, we report the preparation, characterization, comparison and luminescence mechanisms of Eu2+ -doped and Eu2+ ,Dy3+ -co-doped Ba2 MgSi2 O7 (BMSO) phosphors. Prepared phosphors were synthesized via a high temperature solid-state reaction method. All prepared phosphors appeared white. The phase structure, particle size, and elemental analysis were analyzed using X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy-dispersive X-ray (EDX) analysis. The luminescence properties of the phosphors were investigated by thermoluminescence (TL) and photoluminescence (PL). The PL excitation and emission spectra of Ba2 MgSi2 O7 :Eu2+ showed the peak to be around 381 nm and 490 nm respectively. The PL excitation spectrum of Ba2 MgSi2 O7 :Eu2+ Dy3+ showed the peak to be around 341 nm and 388 nm, and the emission spectrum had a broad band around 488 nm. These emissions originated from the 4f6 5d1 to 4f7 transition of Eu2+ . TL analysis revealed that the maximum TL intensity was found at 5 mol% of Eu2+ doping in Ba2 MgSi2 O7 phosphors after 15 min of ultraviolet (UV) light exposure. TL intensity was increased when Dy3+ ions were co-doped in Ba2 MgSi2 O7 :Eu2+ and maximum TL intensity was observed for 2 mol% of Dy3+ . TL emission spectra of Ba1.95 MgSi2 O7 :0.05Eu2+ and Ba1.93 MgSi2 O7 :0.05Eu2+ ,0.02Dy3+ phosphors were found at 500 nm. TL intensity increased with UV exposure time up to 15 min, then decreased for the higher UV radiation dose for both Eu doping and Eu,Dy co-doping. The trap depths were calculated to be 0.54 eV for Ba1.95 MgSi2 O7 :0.05Eu2+ and 0.54 eV and 0.75 eV for Ba1.93 MgSi2 O7 :0.05Eu2+ ,0.02Dy3+ phosphors. It was observed that co-doping with small amounts of Dy3+ enhanced the thermoluminescence properties of Ba2 MgSi2 O7 phosphor. Copyright © 2016 John Wiley & Sons, Ltd. [Correction added on 5 April 2016, after first online publication: The following parts of the abstract have been edited for consistency. '4f65d1' has been corrected to '4f6 5d1 ', '4f7' has been corrected to '4f7 ', 'Ba1.95' has been corrected to 'Ba1.95 ' and 'Ba1.93' has been corrected to 'Ba1.93 ' respectively.].
Subject(s)
Barium/chemistry , Dysprosium/chemistry , Europium/chemistry , Luminescent Agents/chemistry , Magnesium/chemistry , Silicon Compounds/chemistry , Luminescence , Ultraviolet Rays , X-Ray DiffractionABSTRACT
Ce(3+)-doped calcium aluminosilicate phosphor was prepared by a combustion-assisted method at an initiating temperature of 600°C. Structural characterization was carried out using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The absorption spectra of Ca2Al2SiO7:Ce(3+) showed an absorption edge at 230 nm. The optical characterization of Ca2Al2SiO7:Ce(3+) phosphor was investigated in a fracto-mechanoluminescence (FML) and thermoluminescence (TL) study. The peak of ML intensity increased as the height of impact of the moving piston increased. The TL intensity of Ca2Al2SiO7:Ce(3+) was recorded for different exposure times of UV and γ-irradiation and it was observed that TL intensity was maximum for a UV irradiation time of 30 min and for a γ-dose of 1180 Gy. The TL intensity had three peaks for UV irradiation at temperatures 82°C, 125°C and 203°C. Also the TL intensity had a single peak at 152°C for γ-irradiation. The TL and ML emission spectra of Ca2Al2SiO7:Ce(3+) phosphor showed maximum emission at 400 nm. The possible mechanisms involved in the TL and ML processes of the Ca2Al2SiO7:Ce(3+) phosphor are also explained.
