Structural characterization of Er3+,Yb3+‐doped Gd2O3 phosphor,synthesized using the solid‐state reaction method,and its luminescence behavior

We report the synthesis and structural characterization of Er³⁺,Yb³⁺‐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 Er³⁺ and Yb³⁺ 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 Er³⁺ and Yb³⁺‐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). Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis and luminescence study of Eu3+‐doped SrYAl3O7 phosphor

Rare‐earth ions play an important role in eco‐friendly solid‐state lighting for the lighting industry. In the present study we were interested in Eu³⁺ ion‐doped inorganic phosphors for near ultraviolet (UV) excited light‐emitting diode (LED) applications. Eu³⁺ ion‐activated SrYAl₃O₇ phosphors were prepared using a solution combustion route at 550°C. Photoluminescence characterization of SrYAl₃O₇:Eu³⁺ phosphors showed a 612 nm emission peak in the red region of the spectrum due to the ⁵D₀→⁷F₂ transition of Eu³⁺ ions under excitation at 395 nm in the near‐UV region and at the 466 nm blue excitation wavelength. These red and blue emissions are supported for white light generation for LED lighting. Structure, bonding between each element of the sample and morphology of the sample were analysed using X‐ray diffraction (XRD) and scanning electron microscopy (SEM), which showed that the samples were crystallized in a well known structure. The phosphor was irradiated with a ⁶⁰Co‐γ (gamma) source at a dose rate of 7.2 kGy/h. Thermoluminescence (TL) studies of these Eu³⁺‐doped SrYAl₃O₇ phosphors were performed using a Nucleonix TL 1009I TL reader. Trapping parameters of this phosphor such as activation energy (E), order of kinetics (b) and frequency factor (s) were calculated using Chen's peak shape method, the initial rise method and Ilich's method.     

Fracto‐mechanoluminescence and thermoluminescence properties of UV and γ‐irradiated Ca2Al2SiO7:Ce3+ phosphor

Ce³⁺‐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:Ce³⁺ showed an absorption edge at 230 nm. The optical characterization of Ca₂Al₂SiO₇:Ce³⁺ 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:Ce³⁺ 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:Ce³⁺ phosphor showed maximum emission at 400 nm. The possible mechanisms involved in the TL and ML processes of the Ca₂Al₂SiO₇:Ce³⁺ phosphor are also explained. Copyright © 2015 John Wiley & Sons, Ltd.     

Dy3+‐, Sm3+‐, Ce3+‐ and Tb3+‐activated optical properties of microcrystalline BaMgP2O7 phosphors

Photoluminescence (PL) and thermoluminescence (TL) properties of rare earth (RE) ion (RE = Dy³⁺, Sm³⁺, Ce³⁺, Tb³⁺) activated microcrystalline BaMgP₂O₇ phosphors are presented in this work. Non‐doped and doped samples of BaMgP₂O₇ were prepared using a solid state diffusion method and characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), PL and TL. The XRD measurement confirmed the phase purity of the BaMgP₂O₇ host matrix. The average particle size was found through SEM measurement to be around 2 μm. All activators using the PL technique displayed characteristic excitation and emission spectra that corresponded to their typical f → f and f → d transitions respectively. Thermoluminescence measurements showed that BaMgP₂O₇:RE (RE = Dy³⁺, Sm³⁺, Tb³⁺, Ce³⁺) and co‐doped BaMgP₂O₇:Ce³⁺,Tb³⁺ phosphors have also TL behaviour.     

Photoluminescent properties of Eu3+‐Eu2+ activated MAl2SixO2x + 4 (M = Mg,Ca, Sr,Ba) phosphors prepared in air

In this paper, MAl₂Si_xO_2x+4:Eu²⁺/Eu³⁺ (Eu²⁺ + Eu³⁺ = 2%, molar ratio; M = Mg, Ca, Sr, Ba; x = 0, 0.5, 1, 1.5, 2) phosphors with different SiO₂ concentrations (the ratio of SiO₂ to MAl₂O₄ is n%, n = 0, 50, 100, 150, 200, respectively) were prepared by high‐temperature solid‐state reaction under atmospheric air conditions. Their structures and photoluminescent properties were systematically researched. The results indicate that Eu³⁺ ions have been reduced and Eu²⁺ ions are obtained in air through the self‐reduction mechanism. The alkaline earth metal ions and doping SiO₂ strongly affect the crystalline phase and photoluminescent properties of samples, including microstructures, relative intensity of Eu²⁺ to Eu³⁺, location of emission lines/bands. It is interesting and important that the emission color and intensities of europium‐doped various phosphors which consist of aluminosilicate matrices prepared under atmospheric air conditions could be modulated by changing the kinds of alkaline earth metal and the content of SiO₂.     

Investigation of UV‐emitting Gd3+‐doped LiCaBO3 phosphor

Incorporating the Gd³⁺ rare earth ion in the LiCaBO₃ host lattice resulted in narrow‐band UV‐B emission peaking at 315 nm, with excitation at 274 nm. The LiCaBO₃:Gd³⁺ phosphor was synthesized via the solid‐state diffusion method. The structural, morphological and luminescence properties of this phosphor were characterized by X‐ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and photoluminescence (PL) spectroscopy. Electron paramagnetic resonance (EPR) characterization of the as‐prepared phosphors is also reported here. XRD studies confirmed the crystal formation and phase purity of the prepared phosphors. A series of different dopant concentrations was synthesized and the concentration‐quenching effect was studied. Critical energy transfer distance between activator ions was determined and the mechanism governing the concentration quenching is also reported in this paper. Copyright © 2015 John Wiley & Sons, Ltd.     

Structural and optical properties of europium‐ and titanium‐doped Y2O3 nanoparticles

Luminescent nanoparticles of Y₂O₃ doped with europium (Eu) and/or titanium (Ti) were synthesized using modified sol–gel routes. The crystalline cubic phase was confirmed using X‐ray powder diffraction (XRD). Particle morphology and size were evaluated using scanning and transmission electron microscopy. High‐resolution transmission electron microscopy showed that the synthesis method affected the average particle size and the Fourier transform of the images showed the lattice plane distances, indicating that the samples presented high crystallinity degree in accordance with the XRD pattern. The Ti valence was investigated using X‐ray absorption near edge spectroscopy and the tetravalent form was the dominant oxidizing state in the samples, mainly in Eu and Ti co‐doped Y₂O₃. Optical behaviour was investigated through X‐ray excited optical luminescence and photoluminescence under ultraviolet–visible (UV–vis) and vacuum ultraviolet (VUV) excitation. Results indicated that Eu³⁺ is the emitting centre in samples doped with only Eu and with both Eu and Ti with the ⁵D₀→⁷F₂ transition as the most intense, indicating Eu³⁺ in a noncentrosymmetric site. Finally, in the Eu,Ti‐doped Y₂O₃ system, Ti³⁺ (or Ti^IV) excitation was observed but no Ti emission was present, indicating a very efficient energy transfer process from Ti to Eu³⁺. These results can aid the development of efficient nanomaterials, activated using UV, VUV, or X‐rays.     

Synthesis and luminescent properties of Eu(TTA)3·3H2O nanocrystallines

Nanocrystallines of rare earth complex, Eu(TTA)₃·3H₂O, were synthesized by the chemical precipitation method and were characterized by elemental analysis, ultraviolet visible absorption spectroscopy (UV–vis), infrared spectroscopy (IR), differential thermal analysis–thermogravimetry (TG‐DTA), X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The size of the nanocrystallines was tunable by selecting the proper buffer system, which was used to control the pH of the solution. A small polydispersity in particle size ranging from 70 to 250 nm was obtained when ammonia was used. The nanocrystallines showed the characteristic fluorescence of europium ions and energy transfer from the organic ligand to central ions was observed by fluorescence excitation and emission spectroscopy. These nanoparticles of rare earth complexes have potential application in luminescent materials due to their excellent fluorescence properties. Copyright © 2009 John Wiley & Sons, Ltd.     

Luminescence properties of barium – gadolinium–titanate ceramics doped with rare‐earth ions (Eu3+ and Tb3+)

Barium‐gadolinium‐titanate (BaGd₂Ti₄O₁₂) powder ceramics doped with rare‐earth ions (Eu³⁺ and Tb³⁺) were synthesized by a solid‐state reaction method. From the X‐ray diffraction spectrum, it was observed that Eu³⁺ and Tb³⁺:BaGd₂Ti₄O₁₂ powder ceramics are crystallized in the form of an orthorhombic structure. Scanning electron microscopy image shows that the particles are agglomerated and the particle size is about 200 nm. Eu³⁺‐ and Tb³⁺‐doped BaGd₂Ti₄O₁₂ powder ceramics were examined by energy dispersive X‐ray analysis, Fourier transform infrared spectroscopy, photoluminescence and thermoluminescence (TL) spectra. Emission spectra of Eu³⁺‐doped BaGd₂Ti₄O₁₂ powder ceramics showed bright red emission at 613 nm (⁵D₀ → ⁷F₂) with an excitation wavelength λ_exci = 408 nm (⁷F₀ → ⁵D₃) and Tb³⁺:BaGd₂Ti₄O₁₂ ceramic powder has shown green emission at 534 nm (⁵D₄ → ⁷F₅) with an excitation wavelength λ_exci = 331 nm ((⁷F₆ → ⁵D₁). TL spectra show that Eu³⁺ and Tb³⁺ ions affect TL sensitivity. Copyright © 2014 John Wiley & Sons, Ltd.     

Structural,morphological and steady state photoluminescence spectroscopy studies of red Eu3+‐doped Y2O3 nanophosphors prepared by the sol‐gel method

Europium trivalent (Eu³⁺)‐doped Y₂O₃ nanopowders of different concentrations (0.5, 2.5, 5 or 7 at.%) were synthesized by the sol‐gel method, at different pH values (pH 2, 5 or 8) and annealing temperatures (600°C, 800°C or 1000°C). The nanopowders samples were characterized by X‐ray diffraction (XRD), field emission scanning electron microscopy (FE‐SEM), Fourier transform infrared spectroscopy (FT‐IR) and steady state photoluminescence spectroscopy. The effect of pH of solution and annealing temperatures on structural, morphological and photoluminescence properties of Eu³⁺‐doped Y₂O₃ were studied and are discussed. It was found that the average crystallite size of the nanopowders increased with increasing pH and annealing temperature values. The Y₂O₃:Eu³⁺ material presented different morphology and its evolution depended on the pH value and the annealing temperature. Activation energies at different pH values were determined and are discussed. Under ultraviolet (UV) light excitation, Y₂O₃:Eu³⁺ showed narrow emission peaks corresponding to the ⁵D_0–⁷F_J (J = 0, 1, 2 and 3) transitions of the Eu³⁺ ion, with the most intense red emission at 611 assigned to forced electric dipole ⁵D₀→⁷F₂. The emission intensity became more intense with increasing annealing temperature and pH values, related to the improvement of crystalline quality. For the 1000°C annealing temperature, the emission intensity presented a maximum at pH 5 related to the uniform cubic‐shaped particles. It was found that for lower annealing temperatures (small crystallite size) the CTB (charge transfer band) position presented a red shift. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis and characterization of novel europium β‐diketonate organic complexes for solid‐state lighting

Volatile Eu complexes, namely Eu(TTA)₃Phen, Eu_(x)Y_(1‐x)(TTA)₃ Phen; Eu_(x)Tb_(1‐x)(TTA)₃Phen; Eu, europium; Y, yttrium; Tb, Terbium; TTA, thenoyltrifluoroacetone; and Phen, 1,10 phenanthroline were synthesized by maintaining stichiometric ratio. Various characterization techniques such as X‐ray diffraction (XRD), photoluminescence (PL) and thermo gravimetric analysis/differential thermal analysis (TGA/DTA) were carried out for the synthesized complexes. Diffractograms of all the synthesized complexes showed well‐resolved peaks, which revealed that pure and doped organic Eu³⁺ complexes were crystalline in nature. Of all the synthesized complexes, Eu_0.5 Tb_0.5(TTA)₃Phen showed maximum peak intensity, while the angle of maximum peak intensity for all complexes was almost the same with slightly different d‐values. A prominent sharp red emission line was observed at 611 nm when excited with light at 370 nm. It was observed that the intensity of red emissions increased for doped europium complexes Eu_(x)Y_(1‐x)(TTA)₃Phen and Eu_(x)Tb_(1‐x)(TTA)₃ Phen, when compared with Eu complexes. Emission intensity increased in the following order: Eu(TTA)₃Phen > Eu_0.5 Tb_0.5(TTA)₃Phen > Eu_0.4 Tb_0.6(TTA)₃Phen > Eu_0.5Y_0.5(TTA)₃Phen > Eu_0.4Y_0.6(TTA)₃Phen, proving their potential application in organic light‐emitting diodes (OLEDs). TGA showed that Eu complexes doped in Y³⁺ and Tb³⁺ have better thermal stability than pure Eu complex. DTA analysis showed that the melting temperature of Eu(TTA)₃ Phen was lower than doped Eu complexes. These measurements infer that all complexes were highly stable and could be used as emissive materials for the fabrication of OLEDs. Copyright © 2012 John Wiley & Sons, Ltd.     

Eu3+–Eu2+‐doped xAl2O3–ySiO2 and xAl2O3–zMgO composites phosphors

In this paper, the Eu³⁺–Eu²⁺ (4%, molar ratio)‐doped xAl₂O₃–ySiO₂ (x = 0–2.5, y = 1–5) and xAl₂O₃–zMgO (x = 0–1.5, z = 0–3) composites phosphors with different Al₂O₃ to SiO₂ (A/S) and Al₂O₃ to MgO (A/M) ratios were prepared using a high‐temperature solid‐state reaction under air atmosphere. The effects of the A/S and A/M on luminescence properties, crystal structure, electron spin resonance, and Commission Internationale de l’Eclairage chromaticity coordinates of the samples were systematically analyzed. These results indicated that the different A/S and A/M ratios in the matrix effectively affected the crystal phase, degrees of self‐reduction of Eu³⁺, and led the relative emission intensity of Eu²⁺/Eu³⁺ to change and adjust.     

Luminescence study of LiMgBO3:Dy for γ‐ray and carbon ion beam exposure

LiMgBO₃:Dy³⁺, a low Z_eff material was prepared using the solution combustion method and its luminescence properties were studied using X‐ray diffraction (XRD), scanning electron microscopy (SEM), thermoluminescence (TL), photoluminescence (PL), Fourier transform infrared spectroscopy, and electron paramagnetic resonance (EPR) techniques. Reitvield refinement was also performed for the structural studies. The PL emission spectra for LiMgBO₃:Dy³⁺ consisted of two peaks at 478 due to the ⁴F_9/2→⁶H_15/2 magnetic dipole transition and at 572 nm due to the hypersensitive ⁴F_9/2→⁶H_13/2 electric dipole transition of Dy³⁺, respectively. A TL study was carried out for both the γ‐ray‐irradiated sample and the C⁵⁺ irradiated samples and was found to show high sensitivity for both. Moreover the γ‐ray‐irradiated LiMgBO₃:Dy³⁺ sample showed linearity in the dose range 10 Gy to 1 kGy and C⁵⁺‐irradiated samples show linearity in the fluence range 2 × 10¹⁰ to 1 × 10¹¹ ions/cm². In the present study, the initial rise method, various heating rate method, the whole glow curve method, glow curve convolution deconvolution function, and Chen's peak shape method were used to calculate kinetic parameters to understand the TL glow curve mechanism in detail. Finally, an EPR study was performed to examine the radicals responsible for the TL process.     

Ca2Al2SiO7:Ce3+ phosphors for mechanoluminescence dosimetry

A series of Ce³⁺ ion single‐doped Ca₂Al₂SiO₇ 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 Ca₂Al₂SiO₇:Ce³⁺ phosphor showed the characteristic emission of Ce³⁺ peaking at 400 nm (UV–violet) and originating from the Ce³⁺ transitions of 5d‐4f (²F_5/2 and ²F_7/2). The photoluminescence (PL) emission spectra for Ca₂Al₂SiO₇:Ce³⁺ were similar to the ML/TL emission spectra. The mechanism of ML excitation and the suitability of the Ca₂Al₂SiO₇:Ce³⁺phosphor for radiation dosimetry are discussed. Copyright © 2016 John Wiley & Sons, Ltd.     

Structural and luminescence properties of Y2‐xGeMoO8:REx (RE = Eu,Tb) phosphors

Y_2‐xGeMoO₈:RE_x (RE = Eu, Tb) phosphors were synthesized using a facile sol–gel method. The morphology and structure of the phosphors were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X‐ray diffraction (XRD); while their luminescent properties were investigated by photoluminescence (PL) spectrometry. Our results reveal that all of these Y_2‐xGeMoO₈:RE_x (RE = Eu, Tb) phosphors adopted the tetragonal phase, belonging to Scheelite (CaWO₄) structure. The obtained YGeMoO₈:Eu phosphors exhibit a strong emission in the red light range which can be assigned to the ⁵D₀ → ⁷F₂ transition of Eu³⁺ when it is excited at 459 nm. Under 392 and 489 nm excitation, the YGeMoO₈:Tb phosphors present predominant green emission (⁵D₄ → ⁷F₅) at 540 nm. The highest emission of the phosphors can be achieved by adjusting the doping concentration to be 0.25 for Eu³⁺ and 0.15 for Tb³⁺, respectively. The promising luminescence properties of these materials indicate that they can be potentially applied to white‐light‐emitting diodes. Copyright © 2013 John Wiley & Sons, Ltd.     

Luminescence study of Dy or Ce activated LiCaBO3 phosphor for γ‐ray and C5+ ion beam irradiation

The photoluminescence and thermoluminescence characteristics of rare earths (Dy or Ce) activated LiCaBO₃ phosphors have been studied. Phosphors were synthesized by modified solid state synthesis. The phosphors were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) and thermoluminescence (TL) for structural, morphological and luminescence studies. Dy³⁺ activated LiCaBO₃ shows emission at 486 and 577 nm due to ⁴ F_9/2 → ⁶H_15/2 and ⁴ F_9/2 → ⁶H_13/2 transition, respectively, whereas the PL emission spectra of Ce³⁺ activated LiCaBO₃ phosphor shows a broad band peaking at 432 nm, which is due to the transition from 5d level to the ground state of the Ce³⁺ ion. The thermoluminescence study was also carried out for both these phosphors for γ‐ray irradiation and carbon beam irradiation. Linearity was studied for a 0.4–3.1 Rad dose γ‐rays. Linear behaviour over this dose range was observed. Gamma ray‐irradiated phosphors were shown to be negligible fading upon storage. All the samples were also studied for 75 MeV C⁵⁺ ion beam exposure in the range of 3.75 × 10¹² – 7.5 × 10¹³ ion cm^–2 fluence. In addition to this, trapping parameters of all the samples were also calculated using Chen's peak shape method. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis and luminescent properties of novel BaGd2O4:Eu3+ scintillating phosphor

BaGd_2‐xO₄:xEu³⁺ and Ba_1‐yGd_1.79‐2yEu_0.21Na_3yO₄ phosphors were synthesized at 1300°C in air by conventional solid‐state reaction method. Phosphors were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence excitation (PLE) spectra, photoluminescence (PL) spectra and thermoluminescence (TL) spectra. Optimal PL intensity for BaGd_2‐xO₄:xEu³⁺ and Ba_1‐yGd_1.79‐2yEu_0.21Na_3yO₄ phosphors at 276 nm excitation were found to be x = 0.24 and y = 0.125, respectively. The PL intensity of Eu³⁺ emission could only be enhanced by 1.3 times with incorporation of Na⁺ into the BaGd₂O₄ host. Enhanced luminescence was attributed to the flux effect of Na⁺ ions. However, when BaGd₂O₄:Eu³⁺ phosphors were codoped with Na⁺ ions, the induced defects confirmed by TL spectra impaired the emission intensity of Eu³⁺ ions. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis,characterization and luminescence of europium perchlorate with MABA‐Si complex and coating structure SiO2@Eu(MABA‐Si) luminescence nanoparticles

This article reports a novel category of coating structure SiO₂@Eu(MABA‐Si) luminescence nanoparticles (NPs) consisting of a unique organic shell, composed of perchlorate europium(III) complex, and an inorganic core, composed of silica. The binary complex Eu(MABA‐Si)₃·(ClO₄)₃·5H₂O was synthesized using HOOCC₆H₄N(CONH(CH₂)₃Si(OCH₂CH₃)₃)₂ (MABA‐Si) and was used as a ligand. Furthermore, the as‐prepared silica NPs were successfully coated with the ‐Si(OCH₂CH₃)₃ group of MABA‐Si to form Si–O–Si chemical bonds by means of the hydrolyzation of MABA‐Si. The binary complexes were characterized by elemental analysis, molar conductivity and coordination titration analysis. The results indicated that the composition of the binary complex was Eu(MABA‐Si)₃·(ClO₄)₃·5H₂O. Coating structure SiO₂@Eu(MABA‐Si) NPs were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM) and infrared (IR) spectra. Based on the SEM and TEM measurements, the diameter of core‐SiO₂ particles was ~400 and 600 nm, and the thickness of the cladding layer Eu(MABA‐Si) was ~20 nm. In the binary complex Eu(MABA‐Si)₃·(ClO₄)₃·5H₂O, the fluorescence spectra illustrated that the energy of the ligand MABA‐Si transferred to the energy level for the excitation state of europium(III) ion. Coating structure SiO₂@Eu(MABA‐Si) NPs exhibited intense red luminescence compared with the binary complex. The fluorescence lifetime and fluorescence quantum efficiency of the binary complex and of the coating structure NPs were also calculated. The way in which the size of core‐SiO₂ spheres influences the luminescence was also studied. Moreover, the luminescent mechanisms of the complex were studied and explained.     

Characterization and luminescence properties of CaMgSi2O6:Eu2+ blue phosphor

A blue CaMgSi₂O₆:Eu²⁺ 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 Eu²⁺‐doped CaMgSi₂O₆ 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:Eu²⁺ 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:Eu²⁺ phosphors are discussed. Copyright © 2015 John Wiley & Sons, Ltd.     

The structure and luminescence properties of Mn2+/Eu2+/Er3+‐doped MgO‐Ga2O3‐SiO2 glasses and glass‐ceramics

The MgO–Ga₂O₃–SiO₂ glasses and glass‐ceramics samples doped with Eu²⁺/Mn²⁺/Er³⁺ and heated in reductive atmosphere were prepared by the sol–gel method. The structure, morphology and the luminescence properties were studied using X‐ray diffraction, high‐resolution transmission electron microscope, fluorescence spectra, and up‐conversion emission. The luminescence characteristics of doped ions could be influenced by temperature and matrix component. The characteristic emission of Mn²⁺, Eu²⁺ and Er³⁺ were seen and the energy transfer efficiency from Eu²⁺ to Mn²⁺ was enhanced as Mn²⁺ concentration was increased. In addition, the two‐photon process was determined for the Er³⁺‐doped samples.