Luminescence investigation of novel MgPbAl10O17:Tb3+ green‐emitting phosphor for solid‐state lighting

In this work, we studied the luminescence properties of Tb³⁺‐doped MgPbAl₁₀O₁₇ green phosphor. To understand the excitation mechanism and corresponding emission of the prepared phosphor, its structural, morphological and photoluminescence properties were investigated. In general, for green emission, Tb³ is used as an activator and the obtained excitation and emission spectra indicated that this phosphor can be effectively excited by a wavelength of 380 nm, and exhibits bright green emission centered at 545 nm corresponding to the f → f transition of trivalent terbium ions. The chromaticity coordinates were (C_x = 0.263, C_y = 0.723). The impact of Tb³⁺ concentration on the relative emission intensity was investigated, and the best doping concentration was found to be 2 mol%. This study suggests that Tb³⁺‐doped MgPbAl₁₀O₁₇ phosphor is a strong candidate for a green component in phosphor‐converted white light‐emitting diodes. Copyright © 2015 John Wiley & Sons, Ltd.     

Novel optical properties of Ca12Al10.6Si3.4O32Cl5.4:Ce3+,Li+ phosphor for solid‐state lighting

This article reports a novel blue emission in a series of Ca₁₂Al_10.6Si_3.4O₃₂Cl_5.4:Ce³⁺ phosphor under excitation in the near‐UV wavelength range. This phosphor was prepared using the combustion method. Here, the Ce³⁺ emission band is observed over a broad range of 380–550 nm, under 365 nm excitation, and is due to 5d–4f transition. The effect of a Li⁺ charge compensator on the emission properties of the phosphor was also investigated for the first time. X‐Ray diffraction confirmed the phase purity of the synthesized phosphor. The surface morphology and elemental composition of the phosphor were studied using scanning electron microscopy and energy‐dispersive X‐ray spectroscopy. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis and luminescence characterization of Y2BaZnO5:RE (RE = Eu3+, Tb3+, Pr3+ and Sm3+) phosphors

Modified synthesis and luminescence of Y₂BaZnO₅ phosphors activated with the rare earths (RE) Eu³⁺, Tb³⁺, Pr³⁺ and Sm³⁺ are reported. RE₂BaZnO₅ phosphors have attracted attention because of their interesting magnetic and optical properties; and are usually prepared using a two‐step solid‐state reaction. In the first step, carbonates or similar precursors are thoroughly mixed and heated at 900°C to decompose them to oxides. To eliminate the unwanted phases like BaRE₂O₄, the resulting powders are reheated at 1100°C for a long time. We prepared Y₂BaZnO₅ phosphors activated with various activators by replacing the first step with combustion synthesis. The photoluminescence results are presented. The photoluminescence results for Eu³⁺, Tb³⁺ and Pr³⁺ are in good agreement with the literature. However, photoluminescence emission from Sm³⁺ has not been documented previously. The excitation spectrum of Eu³⁺ is dominated by a charge transfer band around 261 nm, and an additional band around 238 nm is always present, irrespective of the type of activator. The presence of this band for all these different types of activators was interpreted as host absorption.     

Photoluminescence properties of a new orange–red‐emitting Sm3+–La3SbO7 phosphor

The antimonate compound La₃SbO₇ has high chemical stability, lattice stiffness and thermal stability. Orange–red‐emitting antimonate‐based phosphors La₃SbO₇:xSm³⁺ (x = 0.02, 0.05, 0.08, 0.10, 0.15, 0.20 and 0.25) were synthesized. The phase structure and photoluminescence properties of these phosphors were investigated. The emission spectrum obtained on excitation at 407 nm contained exclusively the characteristic emissions of Sm³⁺ at 568, 608, 654 and 716 nm, which correspond to the transitions from ⁴G_5/2 to ⁶H_5/2, ⁶H_7/2, ⁶H_9/2 and ⁶H_11/2 of Sm³⁺, respectively. The strongest emission was located at 608 nm due to the ⁴G_5/2→⁶H_7/2 transition of Sm³⁺, generating bright orange–red light. The critical quenching concentration of Sm³⁺ in La₃SbO₇:Sm³⁺ phosphor was determined as 10% and the energy transfer between Sm³⁺ was found to be through an exchange interaction. The International Commission on Illumination chromaticity coordinates of the La₃SbO₇:0.10Sm³⁺ phosphors are located in the orange–red region. The La₃SbO₇:Sm³⁺ phosphors may be potentially used as red phosphors for white light‐emitting diodes. Copyright © 2015 John Wiley & Sons, Ltd.     

Investigation on luminescence properties of Eu2+‐doped Ba3Al2O5Cl2 phosphor for near‐UV‐excited white LEDs

Ba₃Al₂O₅Cl₂:Eu²⁺ phosphor was prepared by combustion synthesis (CS). The prepared phosphor was excited at 329 nm; the phosphors shows an efficient bluish‐green wide‐band emission centred at 490 nm, which originates from the 4f⁶d¹ → 4f⁷ transition of Eu²⁺ ions. The excitation spectra of the phosphors have a band centred at 329 nm. It was also characterized by XRD, FT–IR for confirmation of phase purity, and FT–IR analysis indicated the vibrations of metal–oxygen (M–O) groups. SEM shows the morphology of the phosphor at the submicron scale. The results indicate that Ba₃Al₂O₅Cl₂:Eu²⁺ phosphor may be applicable for solid‐state lighting purposes. Copyright © 2012 John Wiley & Sons, Ltd.     

Luminescence properties of a novel red phosphor 6LaPO4–3La3PO7–2La7P3O18:Eu3+

Eu³⁺‐doped 6LaPO₄–3La₃PO₇–2La₇P₃O₁₈ red luminescent phosphors were synthesized by co‐deposition and high‐temperature solid‐state methods and its polyphase state was confirmed by X‐ray diffraction analysis. Transmission electron microscopy showed the grain morphology as a mixture of rods and spheres. Luminescence properties of the phosphor were investigated and its red emission parameters were evaluated as a function of Eu³⁺ concentration (3.00–6.00 mol%). Excitation spectra of 6LaPO₄–3La₃PO₇–2La₇P₃O₁₈:Eu³⁺ showed strong absorption bands at 280, 395, and 466 nm, while the luminescence spectra exhibited prominent red emission peak centred at 615 nm (⁵D₀→⁷F₂) in the red region. CIE chromaticity coordinates of the 6LaPO₄–3La₃PO₇–2La₇P₃O₁₈:5%Eu³⁺ phosphor were (0.668, 0.313) in the red region, and defined its potential application as a red phosphor.     

Novel blue‐emitting SrMg2Al16O27:Eu2+ phosphor for solid‐state lighting

Eu²⁺‐activated SrMg₂Al₁₆O₂₇ novel phosphor was synthesized by a combustion method (550°C furnace). The prepared phosphor was first characterized by X‐ray diffraction (XRD) for confirmation of phase purity. SEM analysis showed the morphology of the phosphor. The photoluminescence characteristics showed broad‐band excitation at 324 nm, which was monitored at 465 nm emission wavelength. The SrMg₂Al₁₆O₂₇:Eu²⁺ phosphor shows broad blue emission centred at 465 nm, emitting a blue light corresponding to 4f⁶5d¹ → 4f⁷ transition. Here we report the photoluminescence characteristics of the prepared phosphor and compare it with commercial BAM:Eu²⁺ phosphor. Copyright © 2011 John Wiley & Sons, Ltd.     

Photoluminescence and thermoluminescence characteristics of Sr3B2O6:Eu2+ yellow phosphor

Sr₃B₂O₆:Eu²⁺ yellow phosphor was prepared by the combustion method. The crystalline structure, photoluminescence and thermoluminescence properties of Sr₃B₂O₆:Eu²⁺ were investigated extensively. The X‐ray diffraction result indicates that the Sr₃B₂O₆:Eu²⁺ phosphor exhibited a rhombohedral crystal structure. The emission spectra under a 435 nm excited wavelength showed an intense broad band peaking at 574 nm, which corresponds to the 4f⁶5d¹ → 4f⁷ transition of Eu²⁺ ion. There were two different sites of Sr replaced by Eu in host lattice. The concentration quenching process between Eu²⁺ ions is determined and the corresponding concentration quenching mechanism was verified as dipole‐quadrupole interaction. The glow curve under 3 Gy β‐ ray irradiation had the glow peak at 160°C and the average activation energy was defined as about 0.98 eV. Copyright © 2015 John Wiley & Sons, Ltd.     

Photoluminescence properties of a novel phosphor CaB2O4:Eu3+ under NUV excitation

The new borate phosphor CaB₂O₄:Eu³⁺ was synthesized by solid‐state method and their photoluminescence properties were investigated. The results show that the pure phase of CaB₂O₄ could be available at 900°C, CaB₂O₄:Eu³⁺ phosphor could be effectively excited by the near ultraviolet light (NUV) (392 nm), and the luminescent intensity of CaB₂O₄:Eu³⁺ phosphor reached to the highest when the doped‐Eu³⁺ content was 4 mol%. The emission spectra of CaB₂O₄:Eu³⁺ phosphor could exhibit red emission at 612 nm and orange emission at 588 nm, which are ascribed to the ⁵D₀–⁷F₂ and ⁵D₀–⁷F₁ transitions of Eu³⁺ ions. Copyright © 2009 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.     

Photoluminescence properties of LiBaPO4:M3+ phosphor for near‐UV light‐emitting diode (M = Eu and Dy)

A novel phosphor LiBaPO₄ doped with rare earths Eu and Dy prepared by high temperature solid‐state reaction method is reported. The phosphors were characterized by X‐ray powder diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence (PL). The emission and excitation spectra of these materials were measured at room temperature with a spectrofluorophotometer. The excitation spectra of LiBaPO₄:Eu³⁺ phosphor can be efficiently excited by 394 nm, which is matched well with the emission wavelength of near‐UV light‐emitting diode (LED) chip. PL properties of Eu³⁺‐doped LiBaPO₄ exhibited the characteristic red emission coming from ⁵D₀ → ⁷ F₁ (593 nm) and ⁵D₀ → ⁷ F₂ (617 nm) electronic transitions with color co‐ordinations of (0.680, 0.315). The results demonstrated that LiBaPO₄:Eu³⁺ is a potential red‐emitting phosphor for near‐UV LEDs. Emission spectra of LiBaPO₄:Dy³⁺ phosphors showed efficient blue (481 nm) and yellow (574 nm) bands, which originated from ⁴ F_9/2 → ⁶H_15/2 and ⁴ F_9/2 → ⁶H_13/2 transitions of the Dy³⁺ ion, respectively. The 574 nm line is more intense than the 481 nm lines, which indicates that the site Dy³⁺ is located with low symmetry. This article summarizes fundamentals and possible applications of optically useful inorganic phosphates with visible photoluminescence of Eu³⁺ and Dy³⁺ ions. Copyright © 2015 John Wiley & Sons, Ltd.     

Intense green light emission and thermoluminescence glow curve analysis of Tb3+-activated CaY2O4 phosphor

Here, the synthesis and luminescence analysis of the Tb³⁺-activated phosphor were reported. The CaY₂O₄ phosphors were synthesized using a modified solid-state reaction method with a variable doping concentration of Tb³⁺ ion (0.1–2.5 mol%). As synthesized, the phosphor was characterized using Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction analysis techniques for the optimized concentration of doping ions. The prepared phosphor showed a cubic structure, and FTIR analysis confirmed functional group analysis. It was discovered that the intensity of 1.5 mol% was higher than at other concentrations after the photoluminescence (PL) excitation and emission spectra were recorded for different concentrations of doping ions. The excitation was monitored at 542 nm, and the emission was monitored at 237 nm. At 237 nm excitation, the emission peaks were found at 620 nm (⁵D₄→⁷F₃), 582 nm (⁵D₄→⁷F₄), 542 nm (⁵D₄→⁷F₅), and 484 nm (⁵D₄→⁷F₆). The 1931 CIE (x, y) chromaticity coordinates showed the distribution of the spectral region calculated from the PL emission spectra. The values of (x = 0.34 and y = 0.60) were very close to dark green emission. Therefore, the produced phosphor would be very useful for light-emitting diode (green component) applications. Thermoluminescence glow curve analysis for various concentrations of doping ions and various ultraviolet (UV) exposure times was carried out, and a single broad peak was found at 252°C. The computerized glow curve deconvolution method was used to obtain the related kinetic parameters. The prepared phosphor exhibited an excellent response to UV dose and could be useful for UV ray dosimetry.     

Photoluminescence,cathodoluminescence and thermal stability of Sm3+‐activated Sr3La(VO4)3 red‐emitting phosphors

A series of Sm³⁺‐activated Sr₃La(VO₄)₃ phosphors were synthesized by a facile sol‐gel method. X‐ray diffraction patterns and photoluminescence (PL)/cathodoluminescence (CL) spectra as well as PL decay curves were employed to characterize the obtained samples. Upon 402 nm light excitation, the characteristic emissions of Sm³⁺ ions corresponding to ⁴G_5/2→⁶H_J transitions were observed in all the as‐prepared products. The PL emission intensity was increased with increase in Sm³⁺ ion concentration, while concentration quenching occurred when the doping concentration was over 4 mol%. The non‐radiative energy transfer mechanism for concentration quenching of Sm³⁺ ions was dominated by dipole–dipole interaction and the critical distance was around 21.59 Å. Furthermore, temperature‐dependent PL emission spectra revealed that the obtained phosphors possessed good thermal stability with an activation energy of 0.19 eV. In addition, the CL spectra of the samples were almost the same as the PL spectra, and the CL emission intensity showed a tendency to increase with increase in accelerating voltage and filament current. These results suggest that the Sm³⁺‐activated Sr₃La(VO₄)₃ phosphors with good color coordinates, high color purity and superior thermal stability may be a potential candidate for applications in white light‐emitting diodes and field‐emission displays as red‐emitting phosphors.     

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.     

Intensity enhancement of photoluminescence in Tb3+/Eu3+ co-doped Ca14Zn6Al10O35 phosphor for WLEDs

This article focuses on the effect of monovalent cation doping on the optical properties of rare earth (RE = Eu³⁺, Tb³⁺) co-doped Ca₁₄Zn₆Al₁₀O₃₅ which has been synthesized by a low temperature combustion method. Crystalline phase of the Ca₁₄Zn₆Al₁₀O₃₅ phosphor was examined and confirmed by X-ray diffraction measurement. Under near-ultraviolet light excitation Eu³⁺-doped Ca₁₄Zn₆Al₁₀O₃₅ phosphor exhibit characterization of Eu³⁺ emission bands that are located at a maximum wavelength (λ_max) of approximately 470 nm and other peaks centred at 593 nm and 615 nm, respectively. With Tb³⁺-doped Ca₁₄Zn₆Al₁₀O₃₅ phosphor showing a green emission band centred at 544 nm under near-ultraviolet range. Furthermore, we studied the energy transfer process in Eu³⁺/Tb³⁺pair and enhancement in photoluminescence (PL) intensity with doping different charge compensation. Here we obtained the optimum PL emission intensity of the phosphor in broad and intense visible spectral range which may be significant for the fabrication of white light emitting diodes (WLEDs).     

Combustion synthesis of blue‐emitting submicron CaAl4O7:Eu2+, Dy3+ persistence phosphor

Long persistence phosphor CaAl₄O₇: Eu²⁺, Dy³⁺ were prepared by a combustion method. The phosphors were characterized by means of X‐ray diffraction (XRD), scanning electron microscopy (SEM), decay time measurement techniques and photoluminescence spectra (PL). The CaAl₄O₇: Eu²⁺, Dy³⁺ phosphor showed a broad blue emission, peaking at 445 nm when excited at 341 nm. Such a blue emission can be attributed to the intrinsic 4f → 5d transitions of Eu²⁺ in the host lattices. The lifetime decay curve of the Dy³⁺ co‐doped CaAl₄O₇: Eu²⁺ phosphor contains a fast decay component and another slow decay one. Surface morphology also has been studied by SEM. The calculated CIE colour chromaticity coordinates was (0.227, 043). We have also discussed a possible long‐persistent mechanism of CaAl₄O₇:Eu²⁺, Dy³⁺ phosphor. All the results indicate that this phosphor has promising potential for practical applications in the field of long‐lasting phosphors for the purposes of sign boards and defence. Copyright © 2011 John Wiley & Sons, Ltd.     

Luminescence characteristics of Na3Ca2(SO4)3F: Ce3+ fluoride material

A new Na₃Ca₂(SO₄)₃F: Ce³⁺ phosphor synthesized by a solid state diffusion method is reported. The photoluminescence study showed a single high intensity emission peak at 307 nm wavelength when excited by UV light of wavelength 278 nm. An unresolved peak of comparatively less intensity was also observed at 357 nm along with the main peak. The characteristic emission of dopant Ce in Na₃Ca₂(SO₄)₃F phosphor clearly indicated that it resides in the host lattice in trivalent form. The emission peak can be attributed to 5d → 4f transition of rare earth Ce³⁺. The prepared sample is also characterized for its thermoluminescence properties. The TL glow curve of prepared sample showed a single broad peak at 147°C. The trapping parameters are also evaluated by Chen's method. The values of trap depth (E) and frequency factor (s) were found to be 0.64 ± 0.002 eV and 1.43 × 10⁷ s^–1 respectively. The study of PL and TL along with evaluation of trapping parameters has been undertaken and discussed for the first time. Copyright © 2014 John Wiley & Sons, Ltd.     

Study of luminescence and effect of Dy3+ on NaMgSO4Cl:Ce chlorosulphate phosphor

Chlorosulphate NaMgSO₄Cl phosphor doped with Ce³⁺ and co‐doped by Dy³⁺ prepared by the wet chemical method was studied for its photoluminescence and thermoluminescence (TL) characteristics. The emission spectrum of Ce³⁺ shows dominant peaks at 346 nm (excitation 270 nm) due to 5d → 4f transition. Efficient energy transfer occurs from Ce³⁺ → Dy³⁺ ions. Dy³⁺ emission at 485 nm and 576 nm is due to ⁴ F_9/2 → ⁶H_15/2 and ⁴ F_9/2 → ⁶H_13/2 transitions of Dy³⁺ ion respectively. The TL glow curves of NaMgSO₄Cl:Ce and Ce,Dy have been recorded for various concentrations at a heating rate of 2 °C/s irradiated by γ‐rays at a dose rate of 0.995 kGy/h for 1 Gy, which peaks at about 241 °C and 247‐312 °C respectively. Further, in changing the concentration level, the general structure of the intensity is found to increase. The main property of this phosphor is its sensitivity even for low concentrations of rare earth ions and low γ‐ray dose. There is still scope for higher doses of γ‐radiation. The phosphor presented may be used as a lamp phosphor as well as for TL studies. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis and effect of Ce and Mn co‐doping on photoluminescence characteristics of Ca6AlP5O20:Eu novel phosphors

A series of Ca₆AlP₅O₂₀ doped with rare earths (Eu and Ce) and co‐doped (Eu, Ce and Eu,Mn) were prepared by combustion synthesis. Under Hg‐free excitation, Ca₆AlP₅O₂₀:Eu exhibited Eu²⁺ (486 nm) emission in the blue region of the spectrum and under near Hg excitation (245 nm), Ca₆AlP₅O₂₀:Ce phosphor exhibited Ce³⁺ emission (357 nm) in the UV range. Photoluminescence (PL) peak intensity increased in Ca₆AlP₅O₂₀:Eu,Ce and Ca₆AlP₅O₂₀:Eu, Mn phosphors due to co‐activators of Ce³⁺ and Mn²⁺ ions. As a result, these ions played an important role in PL emission in the present matrix. Ca₆AlP₅O₂₀:Eu, Ce and Ca₆AlP₅O₂₀:Eu, Mn phosphors provided energy transfer mechanisms via Ce³⁺ → Eu²⁺ and Eu²⁺ → Mn²⁺, respectively. Eu ions acted as activators and Ce ions acted as sensitizers. Ce emission energy was well matched with Eu excitation energy in the case of Ca₆AlP₅O₂₀:Eu, Ce and Eu ions acted as activators and Mn ions acted as sensitizers in Ca₆AlP₅O₂₀:Eu, Mn. This study included synthesis of new and efficient phosphate phosphors. The impact of doping and co‐doping on photoluminescence properties and energy transfer mechanisms were investigated and we propose a feasible interpretation. Copyright © 2012 John Wiley & Sons, Ltd.     

The high thermal stability of white emitting phosphor Mg2Y2Al2Si2O12:Dy3+,Eu3+,La3+/Lu3+ for white light emitting diodes

A series of Mg₂Y₂Al₂Si₂O₁₂:Dy³⁺,Eu³⁺ was prepared using a solid-state method, and the phosphor emitted white light by tuning the ratio of Dy³⁺/Eu³⁺. The effects of La³⁺/Lu³⁺ on the structure and luminescence properties of Mg₂Y₂Al₂Si₂O₁₂:Dy³⁺,Eu³⁺ were explored. Under the influence of bond length and twist, the luminescence intensity of the materials increased first and then decreased under excitation with ultraviolet light. The lattice distortion of the trivalent cation La³⁺-substituted Mg₂Y₂Al₂Si₂O₁₂:Dy³⁺ and Eu³⁺ phosphors was reduced, the symmetry of polyhedron occupied by the luminescence centre improved, and the thermal stability of the luminescence centre improved to a certain extent. White light emitting diodes (LEDs) were fabricated by combining a 370 nm LED chip and the Mg₂Y₂Al₂Si₂O₁₂:Dy³⁺,Eu³⁺,La³⁺ (Mg₂Y₂Al₂Si₂O₁₂:Dy³⁺,Eu³⁺,Lu³⁺) phosphor. The results showed that Mg₂Y₂Al₂Si₂O₁₂:Dy³⁺,Eu³⁺,La³⁺/Lu³⁺ may have potential application in the area of white LEDs.