Retraction: A study on the luminescence properties of gamma-ray-irradiated white light emitting Ca2Al2SiO7:Dy3+ phosphors fabricated using a combustion-assisted method.

[This retracts the article DOI: 10.1039/C6RA04913C.].

Correction and removal of expression of concern: A study on the luminescence properties of gamma-ray-irradiated white light emitting Ca2Al2SiO7:Dy3+ phosphors fabricated using a combustion-assisted method.

[This corrects the article DOI: 10.1039/C6RA04913C.].

Correction: 3T1R model and tuning of thermoluminescence intensity by optimization of dopant concentration in monoclinic Gd2O3:Er3+;Yb3+ co-doped phosphor.

Correction for '3T1R model and tuning of thermoluminescence intensity by optimization of dopant concentration in monoclinic Gd2O3:Er3+;Yb3+ co-doped phosphor' by Raunak Kumar Tamrakar et al., Phys. Chem. Chem. Phys., 2017, 19, 14680-14694.

Cool white light emission from Dy3+ activated alkaline alumino silicate phosphors.

A series of single phase white light emitting CaSrAl2SiO7:Dy3+ phosphors were prepared by traditional high temperature solid state reaction method. Structural characterization was done by X-ray diffraction, field emission scanning electron microscopy and energy dispersive spectroscopy analyses. Optical characterization was performed from photoluminescence and thermoluminescence studies. When excited at 350 nm, CaSrAl2SiO7:Dy3+ phosphors showed two intense emission bands in the blue region (480 nm and 493 nm) corresponding to 4F9/2 → 6H15/2 transition and one in yellow region (576 nm) corresponding to 4F9/2 → 6H13/2 transition. The Commission Internationale de I'Eclairage diagram was drawn for entire series. It confirmed that by manipulating Dy3+ content the luminescence color of CaSrAl2SiO7:Dy3+ phosphors were tuned from blue to white region. Computation of correlated color temperature suggested that present phosphor was cool in appearance hence CaSrAl2SiO7:Dy3+ phosphor can serve as a white light emitting phosphor and may be useful in outdoor illumination. A detailed study on thermoluminescence of ultraviolet exposed samples was done and possible mechanism of thermoluminescence was discussed. TL emission spectrum was also measured.

Studies on the luminescence properties of cerium co-doping on Ca2 MgSi2 O7 :Eu2+ phosphor by solid-state reaction method.

Ca2 MgSi2 O7 :Ce3+ , Ca2 MgSi2 O7 :Eu2+ and Ca2 MgSi2 O7 :Eu2+ ,Ce3+ phosphors were prepared using the solid-state reaction method. The crystal structures of the sintered phosphors were of melilite type, which has a tetragonal crystallography. The chemical compositions of the sintered phosphors was confirmed by energy dispersive X-ray spectroscopy. The different thermoluminescence kinetic parameters [activation energy (E), frequency factor (s) and order of the kinetics (b)] of these phosphors were evaluated and compared using the peak shape method. Under ultraviolet excitation, the emission spectra of both Ca2 MgSi2 O7 :Eu2+ and Ca2 MgSi2 O7 :Eu2+ ,Ce3+ phosphors were composed of a broad emission band peaking at 530 nm. When the Ca2 MgSi2 O7 :Eu2+ phosphor is co-doped with Ce3+ ions, photoluminescence, afterglow and mechanoluminescence intensity was strongly enhanced. Ca2 MgSi2 O7 :Eu2+ showed some afterglow with a short persist time. On incorporation of Ce3+ , efficient energy transfer from Ce3+ to Eu2+ was found and the emission intensity of Eu2+ was enhanced. The mechanoluminescence intensities of Ca2 MgSi2 O7 :Ce3+ , Ca2 MgSi2 O7 :Eu2+ and Ca2 MgSi2 O7 :Eu2+ ,Ce3+ phosphors increased proportionally increased with the increase in impact velocity, which suggests that these phosphors can be used as sensors to detect stress in an object.

3T1R model and tuning of thermoluminescence intensity by optimization of dopant concentration in monoclinic Gd2O3:Er3+;Yb3+ co-doped phosphor.

Thermoluminescence property of a phosphor is an important parameter that helps to determine the use of a phosphor in various dosimetric applications. In this study, the thermoluminescence behaviour of a monoclinic Gd2O3:Er3+;Yb3+ nanophosphor was studied. Gd2O3:Er3+;Yb3+ nanophosphor was prepared using a combustion synthesis method. Structural characterization was carried out via X-ray diffraction and electron microscopy methods. Herein, thermoluminescence (TL) study and kinetic analysis of the UV- and gamma-irradiated phosphor was also carried out. The prepared phosphor exhibits two TL glow curves around 122 and 263 °C for UV excitation and 157 and 295 °C for gamma exposure. The effect of different parameters on the TL glow curve was investigated. The glow curve deconvolution function was applied on the tuned glow peak curve. The trapping parameters were determined for tuned glow curve peaks as well as for the deconvoluted peaks. Moreover, reproducibility of the sample was determined via 7 replicate TL measurements. The prepared sample shows good reproducibility for both UV and gamma exposure. A theoretical three trap and one recombination centre (3T1R) model was proposed to explain the concentration quenching effect on the thermoluminescence behaviour of the prepared sample.

Synthesis, characterization and thermoluminescence studies of (ZnS)1-x (MnTe)x nanophosphors.

The present paper reports the thermoluminescence (TL) of (ZnS)1-x (MnTe)x nanophosphors that were prepared by a wet chemical synthesis method. The structure investigated by X-ray diffraction patterns confirms the formation of a sphalerite phase whose space group was found to be F 4¯3m. From XRD, TEM and SEM analyses the average sizes of the particles were found to be 12 nm, 11 nm and 15 nm, respectively. Initially the TL intensity increased with increasing values of x because the number of luminescence centres increased; however, for higher values of x the TL intensity decreased because of the concentration quenching. Thus the TL, mechanoluminescence and photoluminescence intensities are optimum for a particular value of x, that is for x = 0.05. Thermoluminescence of the (ZnS)1-x (MnTe)x nanophosphor has not been reported previously. There were two peaks seen in the thermoluminescence glow curves in which the first peak lay at 105-100 °C and the second peak lay at 183.5-178.5 °C. The activation energies for the first and second peaks were found to be 0.45 eV and 0.75 eV, respectively.

INVESTIGATION OF THERMOLUMINESCENCE CHARACTERISTICS OF Y2O3:Er3+ NANOPHOSPHORS.

Thermoluminescence (TL) characteristics of Y2O3:Er3+ nanophosphor exposed to UV radiations were investigated. Combustion synthesis method was employed to synthesise the nanophosphors. The confirmation for the pure cubic phase was done by powder X-ray diffraction. The particles formed were found to have 23.19 nm size and it was calculated by the Debye-Scherrer formula for [222] plane and is in close agreement with those obtained using transmission electron microscopy analysis. scanning electron microscopy micrograph reveals porous, irregular shaped particles with large agglomeration of particles whereas Fourier transform infrared spectroscopy studies confirm the presence of organic residua OH and CO in the samples. TL characteristics of UV irradiated Y2O3:Er3+ for (1-5) mol % were investigated. All the TL glow curves show almost similar glow curves having a single broad peak at 113.26, 113.82 113.72, 113.74 and 113.72°C for 1, 2, 3, 4 and 5 mol %, respectively, of Er3+ ions. The effects of heating rate were also studied and the trapping parameters, namely activation energy (E), order of kinetics (b) and frequency factor (s) were determined using Chen's peak shape method and computerised glow curve deconvolution technique suggested by Kitis for second-order kinetics. They were also discussed in detail for their possible usage in dosimetry.

Ca2 Al2 SiO7 :Ce3+ phosphors for mechanoluminescence dosimetry.

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.

Investigations on luminescence behaviour of Ce-activated BaMgAl10 O17 phosphor.

The present paper describes the synthesis of cerium-doped barium magnesium aluminate phosphor by combustion method. The crystal structure of synthesized phosphor belongs to the P63 /mmc space group and is related to the ß-alumina structure. The photoluminescence emission spectra exhibited a broad peak centered at 440 nm showing the Ce3+ emission. The thermoluminescence properties of phosphors under ultraviolet irradiation were investigated. The activation energy was calculated by Chen's empirical method. Fracto-mechanoluminescence properties were also investigated. The phosphor showed mechanoluminescence (ML) properties without irradiation and the ML intensity increased linearly with the impact height of the moving piston. Therefore this compound may have a use as a damage sensor. Copyright © 2016 John Wiley & Sons, Ltd.

Photoluminescence and thermoluminescence properties of Eu2+ doped and Eu2+ ,Dy3+ co-doped Ba2 MgSi2 O7 phosphors.

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.].

Photoluminescence properties of rare-earth-doped (Er³âº,Yb³âº) Y2O3 nanophosphors by a combustion synthesis method.

In this work, we report the synthesis of Y2O3:Er(3+), Y2O3:Yb(3+) and Y2O3:Er(3+),Yb(3+) nanophosphors by the combustion synthesis method using urea as fuel. The doping agents were incorporated in the form of erbium nitrate and ytterbium nitrate. X-Ray diffraction (XRD) patterns revealed that the synthesized particles have a body-centered cubic structure with space group Ia-3. The photoluminescence (PL) properties were investigated after UV and infrared irradiation at room temperature. A strong characteristic emission of Er(3+) and Yb(3+) ions was identified, and the influence of doping concentration on the PL properties was systematically studied. Energy transfer from Yb(3+) to Er(3+) ions was observed in Y2O3 nanophosphors. The obtained result may be useful in potential applications such as bioimaging.

Fracto-mechanoluminescence and thermoluminescence properties of UV and γ-irradiated Ca2Al2SiO7:Ce³âº phosphor.

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.

Mechanoluminescence properties of SrAl2O4:Eu(2+) phosphor by combustion synthesis.

In this paper, europium-doped strontium aluminate (SrAl2O4:Eu(2+)) phosphors were synthesized using a combustion method with urea as a fuel at 600°C. The phase structure, particle size, surface morphology and elemental analysis were studied using X-ray diffractometry (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX) and Fourier transform infrared (FTIR) spectra. The EDX and FTIR spectra confirm the elements present in the SrAl2O4:Eu(2+) phosphor. The optical properties of SrAl2O4:Eu(2+) phosphors were investigated by photoluminescence (PL) and mechanoluminescence (ML). The excitation and emission spectra showed a broad band with peaks at 337 and 515 nm, respectively. The ML intensities of SrAl2O4:Eu(2+) phosphor increased proportionally with the increase in the height of the mechanical load, which suggests that this phosphor could be used in stress sensors. The CIE colour chromaticity diagram and ML spectra confirm that the SrAl2O4:Eu(2+) phosphor emitted green coloured light.

Structural characterization of Er(3+),Yb(3+)-doped Gd2O3 phosphor, synthesized using the solid-state reaction method, and its luminescence behavior.

We report the synthesis and structural characterization of Er(3+),Yb(3+)-doped Gd2O3 phosphor. The sample was prepared using the conventional solid-state reaction method, which is the most suitable method for large-scale production. The prepared phosphor sample was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), thermoluminescence (TL), photoluminescence (PL) and CIE techniques. For PL studies, the excitation and emission spectra of Gd2O3 phosphor doped with Er(3+) and Yb(3+) were recorded. The excitation spectrum was recorded at a wavelength of 551 nm and showed an intense peak at 276 nm. The emission spectrum was recorded at 276 nm excitation and showed peaks in all blue, green and red regions, which indicate that the prepared phosphor may act as a single host for white light-emitting diode (WLED) applications, as verified by International de I'Eclairage (CIE) techniques. From the XRD data, the calculated average crystallite size of Er(3+) and Yb(3+) -doped Gd2O3 phosphor is ~ 38 nm. A TL study was carried out for the phosphor using UV irradiation. The TL glow curve was recorded for UV, beta and gamma irradiations, and the kinetic parameters were also calculated. In addition, the trap parameters of the prepared phosphor were also studied using computerized glow curve deconvolution (CGCD).

Persistent luminescence of CaMgSi2O6:Eu(2+),Dy(3+) and CaMgSi2O6:Eu(2+),Ce(3+) phosphors prepared using the solid-state reaction method.

CaMgSi2O6:Eu(2+),Dy(3+) and CaMgSi2O6:Eu(2+),Ce(3+) phosphors were synthesized using the solid-state reaction method. X-Ray diffraction (XRD) and photoluminescence (PL) analyses were used to characterize the phosphors. The XRD results revealed that the synthesized CaMgSi2O6:Eu(2+),Dy(3+) and CaMgSi2O6:Eu(2+),Ce(3+) phosphors were crystalline and are assigned to the monoclinic structure with a space group C2/c. The calculated crystal sizes of CaMgSi2O6:Eu(2+),Dy(3+) and CaMgSi2O6:Eu(2+),Ce(3+) phosphors with a main (221) diffraction peak were 44.87 and 53.51 nm, respectively. Energy-dispersive X-ray spectroscopy (EDX) confirmed the proper preparation of the sample. The PL emission spectra of CaMgSi2O6:Eu(2+),Dy(3+) and CaMgSi2O6:Eu(2+),Ce(3+) phosphors have a broad band peak at 444.5 and 466 nm, respectively, which is due to electronic transition from 4f(6) 5d(1) to 4f(7). The afterglow results indicate that the CaMgSi2O6:Eu(2+),Dy(3+) phosphor has better persistence luminescence than the CaMgSi2O6:Eu(2+),Ce(3+) phosphor.

Photoluminescence and thermoluminescence studies of CaAl2O4:Dy(3+) phosphor.

Calcium aluminate phosphors activated by Dy(3+) have been prepared by a combustion method at a temperature of 600°C. Photoluminescence (PL) and thermoluminescence (TL) properties of gamma-irradiated Dy-doped calcium aluminate were investigated. The PL spectrum shows a broad peak around 488 nm and 573 nm, under 347 nm excitation. Thermoluminescence studies were performed for different concentrations of Dy. Optimum intensity of photoluminescence was found for 0.02 mol% concentration of Dy. It was found that initially the peak TL intensity increases with increasing concentration of Dy in the CaAl2O4 host, attains a maximum value for 0.05 mol% concentration and decreases with further increase in the doping concentration due to concentration quenching.

Enhancement of the photoluminescence and long afterglow properties of Sr2MgSi2O7:Eu(2+) phosphor by Dy(3+) co-doping.

Sr2MgSi2O7:Eu(2+) and Sr2MgSi2O7:Eu(2+),Dy(3+) long afterglow phosphors were synthesized under a weak reducing atmosphere by the traditional high temperature solid state reaction method. The synthesized phosphors were characterized by powder X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), and photo-, thermo- and mechanoluminescence spectroscopic techniques. The phase structure of the sintered phosphor was an akermanite type structure, which belongs to tetragonal crystallography. The thermoluminescence properties of these phosphors were investigated and compared. Under ultraviolet light excitation, the emission spectra of both prepared phosphors were composed of a broad emission band peaking at 470 nm. When the Sr2MgSi2O7:Eu(2+) phosphor was co-doped with Dy(3+), the photoluminescence (PL), afterglow and mechanoluminescence (ML) intensity were strongly enhanced. The decay graph indicated that both the sintered phosphors contained fast decay and slow decay processes. The ML intensities of Sr2MgSi2O7:Eu(2+) and Sr2MgSi2O7:Eu(2+),Dy(3+) phosphors were increased proportionally with increasing impact velocity, a finding that suggests that these phosphors could be used as sensors to detect the stress of an object.

Characterization and luminescence properties of CaMgSi2O6:Eu2+ blue phosphor.

A blue CaMgSi2O6:Eu(2+) phosphor was prepared by the solid-state reaction method and the phosphor characterized in terms of crystal structure, particle size, photoluminescence (PL), thermoluminescence (TL) and mechanoluminescence (ML) properties using X-ray diffraction (XRD), transmission electron microscopy (TEM), PL spectroscopy, TLD reader and ML impact technique. The XRD result shows that phosphor is formed in a single phase and has a monoclinic structure with the space group C2/c. Furthermore, the PL excitation spectra of Eu(2+) -doped CaMgSi2 O6 phosphor showed a strong band peak at 356 nm and the PL emission spectrum has a peak at 450 nm. The depths and frequency factors of trap centers were calculated using the TL glow curve by deconvolution method in which the trap depths were found to be 0.48 and 0.61 eV. The formation of CaMgSi2O6:Eu(2+) phosphor was confirmed by Fourier transform infrared spectroscopy. The ML intensity increased linearly with the impact velocity of the piston used to deform the phosphor. It was shown that the local piezoelectricity-induced electron bombardment model is responsible for the ML emission. Finally, the optical properties of CaMgSi2O6:Eu(2+) phosphors are discussed.

Luminescence properties of green-emitting Ca2MgSi2O7:Eu2+ phosphor by a solid-state reaction method.

A europium (Eu)-doped di-calcium magnesium di-silicate phosphor, Ca2MgSi2O7 :Eu(2+) , was prepared using a solid-state reaction method. The phase structure, particle size, surface morphology, elemental analysis, different stretching mode and luminescence properties were analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM) with energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared (FTIR) spectroscopy, photoluminescence (PL) and mechanoluminescence (ML). The phase structure of Ca2MgSi2O7:Eu(2+) was an akermanite-type structure, which belongs to the tetragonal crystallography with space group P4̅21 m; this structure is a member of the melilite group and forms a layered compound. The surface of the prepared phosphor was not found to be uniform and particle distribution was in the nanometer range. EDX and FTIR confirm the components of Eu(2+)-doped Ca2MgSi2O7 phosphor. Under UV excitation, the main emission peak appeared at 530 nm, belonging to the broad emission ascribed to the 4f(6) 5d(1) → 4f(7) transition of Eu(2+). The ML intensity of the prepared phosphor increased linearly with increasing impact velocity. A CIE color chromaticity diagram and ML spectrum confirmed that the prepared Ca2MgSi2O7:Eu(2+) phosphor would emit green color and the ML spectrum was similar to that of PL, which indicated that ML is emitted from the same center of Eu(2+) ions.