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.     

Luminescence properties of Tb3+ doped Sr2SnO4 green phosphor in UV/VUV regions

Polycrystalline Sr₂SnO₄ phosphors doped with Tb³⁺ were prepared by conventional solid‐state reaction method. Materials were characterized by powder XRD and EDS techniques. The luminescence properties of these materials were investigated under UV and VUV excitation. Upon excitation at 272 nm, phosphors exhibited intense emissions at 492 and 543 nm due to ⁵D₄ → ⁷ F₆ and ⁵D₄ → ⁷ F₅ transitions of Tb³⁺ ions, respectively. Materials also exhibited strong emissions from these transitions under VUV excitation at 147, 173 and 230 nm. Quantitative analysis of the spectra indicated probable applications of these phosphors for PDP and other display devices as green emitting phosphors. Copyright © 2012 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.     

A novel reddish‐orange phosphor,NaLi2PO4:Eu3+

A series of Eu³⁺‐activated NaLi₂PO₄ novel phosphors was synthesized by the solid‐state reaction method. The X‐ray diffraction (XRD) and photoluminescence (PL) properties of these phosphors were investigated at room temperature. The excitation spectra indicate that these phosphors can be effectively excited by near‐UV (370–410 nm) light. The emission spectra exhibit strong reddish‐orange performance, which is due to the ⁵D₀ → ⁷F_J transitions of Eu³⁺ ions. The orange emission from transition ⁵D₀ → ⁷F₁ is dominant over that of ⁵D₀ → ⁷F_2. The concentration quenching of Eu³⁺ was observed in NaLi₂PO₄:Eu³⁺ when the Eu concentration was at 1 mol%. The impact of doping Eu³⁺ and photoluminescence properties were investigated and we propose a feasible interpretation. Copyright © 2012 John Wiley & Sons, Ltd.     

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.     

Photoluminescence enhancement in Na3SO4Cl:X (X = Ce3+, Eu3+ or Dy3+) material

The compound Na₃SO₄Cl X (X = Ce³⁺, Eu³⁺ or Dy³⁺) prepared by the wet chemical method was studied for its photoluminescence (PL) and energy transfer characteristics. The PL from Na₃SO₄Cl:Ce³⁺ shows strong emission at 322 nm at an excitation of 272 nm. Therefore, an efficient Ce³⁺ → Dy³⁺, Eu²⁺ → Dy³⁺ and Eu²⁺ → Eu³⁺ energy transfer had taken place in this host. The Dy³⁺ emission caused by Ce³⁺ → Dy³⁺ energy transfer under ultraviolet (UV) wavelengths peaked at around 477 nm and 572 nm due to ⁴ F_9/2 → ⁶H_15/2 and ⁶H_13/2 transitions with yellow–orange emission in the Na₃SO₄Cl lattice. An intense Dy³⁺ emission was observed at 482 and 576 nm caused by the Eu²⁺ → Dy³⁺ energy transfer process and due to ⁴ F_9/2 → ⁶H_15/2 and ⁴ F_9/2 → ⁶H_13/2 transitions respectively. The Eu³⁺ blue to red light emission caused by the Eu²⁺ → Eu³⁺ energy transfer peaked at 593 nm and 617 nm due to ⁵D₀ → ⁵D₃ transitions. The presence of trivalent Eu in Na₃SO₄Cl suggested the presence of Eu³⁺ in the host compound that occupied two different lattice sites and that peaked at 593 and 617 nm due to ⁵D₀ → ⁷ F₁ and ⁵D₀ → ⁷ F₂ transitions respectively. The trivalent europium ion is very useful for studying the nature of metal coordination in various systems due to its non‐degenerate emitting ⁵D₀ state. The present paper discusses the photoluminescence characteristics of Eu²⁺ → Dy³⁺ and Eu²⁺ → Eu³⁺ energy transfer. This compound may be useful as a lamp phosphor. Copyright © 2015 John Wiley & Sons, Ltd.     

Optical analysis of RE3+ (RE = Eu,Tb):MgLa2V2O9 nano-phosphors

Red and green rare-earth ion (RE³⁺) (RE = Eu, Tb):MgLa₂V₂O₉ micro-powder phosphors were produced utilizing a standard solid-state chemical process. The X-ray diffraction examination performed on the phosphors showed that they were crystalline and had a monoclinic structure. The particles grouped together, as shown in the scanning electron microscopy (SEM) images. Powder phosphors were examined using a variety of spectroscopic techniques, including photoluminescence (PL), Fourier-transform infrared, and energy dispersive X-ray spectroscopy. Brilliant red emission at 615 nm (⁵D₀ → ⁷F₂) having an excitation wavelength (λ_exci) of 396 nm (⁷F₀ → ⁵L₆) and green emission at 545 nm (⁵D₄ → ⁷F₅) having an λ_exci = 316 nm (⁵D₄ → ⁷F₂) have both been seen in the emission spectra of Tb³⁺:MgLa₂V₂O₉ nano-phosphors. The emission mechanism that is raised in Eu³⁺:MgLa₂V₂O₉ and Tb³⁺:MgLa₂V₂O₉ powder phosphors has been explained in an energy level diagram.     

Emission analysis of Tb3+‐and Sm3+‐ion‐doped (Li2O/Na2O/K2O) and (Li2O + Na2O/Li2O + K2O/K2O + Na2O)‐modified borosilicate glasses

Four series of borosilicate glasses modified by alkali oxides and doped with Tb³⁺ and Sm³⁺ ions were prepared using the conventional melt quenching technique, with the chemical composition 74.5B₂O₃ + 10SiO₂ + 5MgO + R + 0.5(Tb₂O₃/Sm₂O₃) [where R = 10(Li₂O /Na₂O/K₂O) for series A and C, and R = 5(Li₂O + Na₂O/Li₂O + K₂O/K₂O + Na₂O) for series B and D]. The X‐ray diffraction (XRD) patterns of all the prepared glasses indicate their amorphous nature. The spectroscopic properties of the prepared glasses were studied by optical absorption analysis, photoluminescence excitation (PLE) and photoluminescence (PL) analysis. A green emission corresponding to the ⁵D₄ → ⁷F₅ (543 nm) transition of the Tb³⁺ ions was registered under excitation at 379 nm for series A and B glasses. The emission spectra of the Sm³⁺ ions with the series C and D glasses showed strong reddish‐orange emission at 600 nm (⁴G_5/2 →⁶H_7/2) with an excitation wavelength λ_exci = 404 nm (⁶H_5/2→⁴F_7/2). Furthermore, the change in the luminescence intensity with the addition of an alkali oxide and combinations of these alkali oxides to borosilicate glasses doped with Tb³⁺ and Sm³⁺ ions was studied to optimize the potential alkali‐oxide‐modified borosilicate glass.     

Photoluminescence properties of Ca2Al2O5:RE3+ (RE = Eu,Dy and Tb) phosphors for solid state lighting

Ca₂Al₂O₅:Eu³⁺, Ca₂Al₂O₅:Dy³⁺ and Ca₂Al₂O₅:Tb³⁺ phosphors were synthesized using a combustion synthesis method. The prepared phosphors were characterized by X‐ray powder diffraction for phase purity, by scanning electron microscopy for morphology, and by photoluminescence for emission and excitation measurements. The Ca₂Al₂O₅:Eu³⁺ phosphors could be efficiently excited at 396 nm and showed red emission at 594 nm and 616 nm due to ⁵D₀ → ⁷F₁ and ⁵D₀ → ⁷F₂ transitions. Dy³⁺‐doped phosphors showed blue emission at 482 nm and yellow emission at 573 nm. Ca₂Al₂O₅:Tb³⁺ phosphors showed emission at 545 nm when excited at 352 nm. Concentration quenching occurred in both Eu³⁺ and Dy³⁺phosphors at 0.5 mol%. Photoluminescence results suggested that the aluminate‐based phosphor could be a potential candidate for application in environmentally friendly based lighting technologies.     

Photoluminescence properties of LiTi2 − xEux(PO4)3 phosphor

A solid‐state reaction route‐based LiTi_{2 ? x}Eu_x(PO₄)₃ was phosphor synthesized for the first time to evaluate its luminescence performance by excitation, emission and lifetime (τ) measurements. The LiTi_{2 ? x}Eu_x(PO₄)₃ phosphor was excited at λ_exci. = 397 nm to give an intense orange–red (597 nm) emission attributed to the ⁵D₀ → ⁷F₁ magnetic dipole (ΔJ = ±1) transition and red (616 nm) emission (⁵D₀ → ⁷F₂), which is an electric dipole (ΔJ = ±2) transition of the Eu³⁺ ion. Beside this, excitation and emission spectra of host LiTi₂(PO₄)₃ powder were also reported. The effect of Eu³⁺ concentration on luminescence characteristics was explained from emission and lifetime profiles. Concentration quenching in the LiTi_{2 ? x}Eu_x(PO₄)₃ phosphor was studied from the Dexter's model. Dipole–quadrupole interaction is found to be responsible for energy transfer among Eu³⁺ ions in the host lattice. The LiTi_{2 ? x}Eu_x(PO₄)₃ phosphor displayed a reddish‐orange colour realized from a CIE chromaticity diagram. We therefore suggest that this new phosphor could be used as an optical material of technological importance in the field of display devices. Copyright © 2016 John Wiley & Sons, Ltd.     

Photoluminescence properties of aeschynite‐type LaNbTiO6:RE3+ (RE = Tb,Dy, Ho) down‐converting phosphors

In this study, a series of LaNbTiO₆:RE³⁺ (RE = Tb, Dy, Ho) down‐converting phosphors were synthesized using a modified sol–gel combustion method, and their photoluminescence (PL) properties were investigated as a function of activator concentration and annealing temperature. The resultant particles were characterized using X‐ray diffraction, transmission electron microscopy, scanning electron microscopy, UV/Vis diffuse reflectance spectroscopy and PL spectra. The highly crystalline LaNbTiO₆:RE³⁺ (RE = Tb, Dy, Ho) phosphors with an average size of 200–300 nm obtained at 1100°C have an orthorhombic aeschynite‐type structure and exhibit the highest luminescent intensity in our study range. The emission spectra of LaNbTiO₆:RE³⁺ (RE = Tb, Dy, Ho) phosphors under excitations at UV/blue sources are mainly composed of characteristic peaks arising from the f–f transitions of RE³⁺, including 489 nm (⁵D₄ → ⁷F₆) and 545 nm (⁵D₄ → ⁷F₅) for Tb³⁺, 476 and 482 nm (⁴F_9/2 → ⁶H_15/2) and 571 nm (⁴F_9/2 → ⁶H_13/2) for Dy³⁺, and 545 nm (⁵F₄ + ⁵S₂ → ⁵I₈) for Ho³⁺, respectively. The luminescent mechanisms were further investigated. It can be expected that these phosphors are of intense interest and potential importance for many optical applications. Copyright © 2013 John Wiley & Sons, Ltd.     

Luminescent properties of MAl(SO4)2Br:Eu3+ (M = Sr or Mg) red phosphors for near‐UV light‐emitting diodes

Eu³⁺‐activated MAl(SO₄)₂Br phosphors (where M = Mg or Sr) are successfully prepared using a wet chemical reaction technique. The samples are characterized by X‐ray diffraction (XRD) and photoluminescence (PL) spectroscopies. The XRD pattern revealed that both the samples are microcrystalline in nature. PL of Eu³⁺‐doped SrAl(SO₄)₂Br and MgAl(SO₄)₂Br phosphors exhibited characteristic red emission coming from the ⁵D₀ → ⁷F₂ (616 nm) electron transition, when excited by 396 nm wavelength of light. The maximum intensity of luminescence was observed at a concentration of 1 mol% Eu³⁺. The intensity of the electric dipole transition at 616 nm is greater than that of the magnetic dipole transition at 594 nm. The results showed that MAl(SO₄)₂Br:Eu³⁺, (M = Mg, Sr) phosphors have potential application in near‐UV light‐emitting diodes as efficient red‐emitting phosphor. Copyright © 2014 John Wiley & Sons, Ltd.     

Tunable luminescence properties and energy transfer in LaAl11O18:Eu,Tb phosphor

Eu²⁺ and Tb³⁺ singly doped and co‐doped LaAl₁₁O₁₈ phosphors were prepared by a combustion method using urea as a fuel. The phase structure and photoluminescence (PL) properties of the prepared phosphors were characterized by powder X‐ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence excitation and emission spectra. When the content of Eu²⁺ was fixed at 0.01, the emission chromaticity coordinates could be adjusted from blue to green region by tuning the contents of Tb³⁺ ions from 0.01 to 0.03 through an energy transfer (ET) process. The fluorescence data collected from the samples with different contents of Tb³⁺ into LaAl₁₁O₁₈: Eu, show the enhanced green emission at 545 nm associated with ⁵D₄ –⁷F₅ transitions of Tb³⁺. The enhancement was attributed to ET from Eu²⁺ to Tb³⁺, and therefore Eu²⁺ ion acts as a sensitizer (an energy donor) while Tb³⁺ ion as an activator. The ET from Eu²⁺ to Tb³⁺ is performed through dipole–dipole interaction. The ET efficiency and critical distance were also calculated. The present Eu²⁺–Tb³⁺ co‐doped LaAl₁₁O₁₈ phosphor will have potential application for UV convertible white light‐emitting diodes. Copyright © 2015 John Wiley & Sons, Ltd.     

Energy transfer between Ce3+ → Gd3+ or Tb3+ in KNaSO4 microphosphor

KNaSO₄ microphosphor doped with Ce,Gd and Ce,Tb and prepared by a wet chemical method was studied using X‐ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence (PL) characterization. KNaSO₄ has a 5‐µm particle size detected by SEM. KNaSO₄:Ce³⁺,Tb³⁺ showed blue and green emission (at 494 nm, 557 nm, 590 nm) of Tb³⁺ due to ⁵D₄ → ⁷F_J (J = 4, 5, 6) transitions. KNaSO₄:Ce³⁺,Gd³⁺ showed luminescence in the ultraviolet (UV) light region at 314 nm for an excitation at 271 nm wavelength. It was observed that efficient energy transfer took place from Ce³⁺ → Gd³⁺ and Ce³⁺ → Tb³⁺ sublattices indicating that Ce³⁺ could effectively sensitize Gd³⁺ or Tb³⁺ (green emission). Ce³⁺ emission weakened and Gd³⁺ or Tb³⁺ enhanced the emission significantly in KNaSO₄. This paper discusses the development and understanding of photoluminescence and the effect of Tb³⁺ and Gd³⁺ on KNaSO₄:Ce³⁺. Copyright © 2015 John Wiley & Sons, Ltd.     

Luminescence of Eu and Ce in K3Ca2(SO4)3F fluoride material

A new halophosphor K₃Ca₂(SO₄)₃ F activated by Eu or Ce and K₃Ca₂(SO₄)₃ F:Ce,Eu co‐doped halosulfate phosphor has been synthesized by the co‐precipitation method and characterized for its photoluminescence (PL). The PL emission spectra of the K₃Ca₂(SO₄)₃ F :Ce phosphor show emission at 334 nm when excited at 278 nm due to 5d → 4f transition of Ce³⁺ ions. In the K₃Ca₂(SO₄)₃ F:Eu lattice, Eu²⁺ (440 nm) as well as Eu³⁺ (596 nm and 615 nm) emissions have been observed showing ⁵D₀ → ⁷ F₁ and ⁵D₀ → ⁷ F₂ transition of the Eu³⁺ ion, which is in the blue and red region of the visible spectrum respectively. The trivalent europium ion is very useful for studying the nature of metal coordination in various systems owing to its non‐degenerate emitting ⁵D₀ state. K₃Ca₂(SO₄)₃ F:Ce,Eu is suitable for Ce³⁺ → Eu²⁺ → Eu³⁺ energy transfer in which Ce³⁺and Eu²⁺ play the role of sensitizers and Eu²⁺ and Eu³⁺ act as the activators. The observations presented in this paper are relevant for lamp phosphors. Copyright © 2015 John Wiley & Sons, Ltd.     

Preparation and luminescence properties of KLaSiO4:Tb3+ phosphors

KLaSiO₄:Tb³⁺ phosphors were synthesized using the sol–gel method. The structure and luminescence properties of the materials were characterized using X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, thermogravimetry–differential thermal analysis, fluorescence spectra and calculated Commission Internationale de l'éclairage coordinates. The results showed that the material had a hexagonal structure, and that doping of Tb³⁺ did not change the crystal structure of KLaSiO₄. FTIR spectroscopy confirmed the existence of stretching vibrations of Si–O, bending vibrations of Si–O–Si, and asymmetric tensile vibrations of Si–O in KLaSiO₄. The excitation spectrum of the sample consisted of 4f⁷→5d¹ broadband absorption and the characteristic excitation peak of Tb³⁺, the excitation peak at 232 nm belongs to the spin allowed ⁷F_J→⁷D_J transition of Tb³⁺, the excitation peak at 268 nm belongs to the spin forbidden ⁷F_J→⁹D_J transition of Tb³⁺, and the absorption band of ⁷F_J→⁷D_J transition is split. Under excitation at 232 nm, the emission peak of the sample was composed of the ⁵D₄→⁷F_J (J = 6, 5, 4, 3) energy level transition of Tb³⁺. The highest emission peak is located at 543 nm, which belongs to the ⁵D₄→⁷F₅ transition and emits green light. Concentration quenching occurred when the Tb³⁺ doping concentration was greater than 1% mol, the quenching mechanism was an electric dipole–electric dipole action. When the ratio of citric acid to total metal ions was 1:1 and the annealing temperature was 800°C, the surface defects of the phosphors were greatly reduced, the quenching effect was reduced, and the luminous intensity reached the maximum.     

Luminescent properties and energy transfer in the green phosphors LaBSiO5:Tb3+,Ce3+

LaBSiO₅ phosphors doped with Ce³⁺ and Tb³⁺ were synthesized using the conventional solid‐state method at 1100 °C. The phase purity and luminescent properties of these phosphors are investigated. LaBSiO₅:Tb³⁺ phosphors show intense green emission, and LaBSiO₅ phosphors doped with Ce³⁺ show blue–violet emission under UV light excitation. LaBSiO₅ phosphors co‐doped with Ce³⁺ and Tb³⁺ exhibit blue–violet and green emission under excitation by UV light. The blue–violet emission is due to the 5d–4f transition of Ce³⁺ and the green emission is ascribed to the ⁵D₄ → ⁷ F₅ transition of Tb³⁺. The spectral overlap between the excitation band of Tb³⁺ and the emission band of Ce³⁺ supports the occurrence of energy transfer from Ce³⁺ to Tb³⁺, and the energy transfer process was investigated. Copyright © 2014 John Wiley & Sons, Ltd.     

Optical properties of CaAl(SO4)2Br:RE (RE = Dy,Eu, Ce) novel phosphors

A new phosphor CaAl(SO₄)₂Br doped with Dy, Ce and Eu is reported. Rare earth (Dy, Eu and Ce)‐doped polycrystalline CaAl(SO₄)₂Br phosphors were prepared using a wet chemical reaction method and studied for X‐ray diffraction and photoluminescence (PL) characteristics. Dy³⁺ emission in the CaAl(SO₄)₂Br lattice was observed at 484 and 574 nm in the blue and yellow regions of the spectrum, which are assigned to ⁴ F_9/2 → ⁶H_15/2 and ⁴ F_9/2 → ⁶H_13/2 transitions of the Dy³⁺ ion, respectively. While the PL emission spectra of CaAl(SO₄)₂Br:Ce phosphor showed Ce³⁺ emission at 347 nm due to 5d → 4f transition of the Ce³⁺ ion. In a CaAl(SO₄)₂Br:Eu lattice, Eu³⁺ emissions were observed at 593 and 617 nm, coming from the ⁵D₀ → ⁷ F₁ and ⁵D₀ → ⁷ F₂ electron transitions, respectively. The PL study showed that the intensity of electric dipole transition at 617 nm dominates over that of magnetic dipole transition at 590 nm. The maximum PL intensity was obtained for a 1 mol% concentration of Eu³⁺ in CaAl(SO₄)₂Br host lattice. The results showed that the material may be a promising candidate as a blue‐, yellow‐ and red‐emitting phosphor. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis and photoluminescence characteristics of (Y,Gd)BO3:RE (RE = Eu3+, Ce3+, Dy3+ and Tb3+) phosphors for blue chip and near‐UV white LEDs

A series of Eu³⁺‐, Ce³⁺‐, Dy³⁺‐ and Tb³⁺‐doped (Y,Gd)BO₃ phosphors was synthesized by a solid‐state diffusion method. X‐Ray diffraction confirmed their hexagonal structure and the scanning electron microscopy results showed crystalline particles. The excitation spectra revealed that (Y,Gd)BO₃ phosphors doped with Eu³⁺, Ce³⁺ , Dy³⁺ and Tb³⁺ are effectively excited with near UV‐light of 395 nm/blue light, 364, 351 and 314 nm, respectively. Photoluminescence spectra of Eu³⁺‐, Ce³⁺‐ and Tb³⁺/Dy³⁺‐doped phosphor showed intense emission of reddish orange, blue and white light, respectively. The phosphor Y_0.60Gd_0.38BO₃:Ce_0.02 showed CIE 1931 color coordinates of (0.158, 0.031) and better color purity compared with commercially available blue BAM:Eu²⁺ phosphor. The phosphor (Y,Gd)BO₃ doped with Eu³⁺, Dy³⁺ and Tb³⁺ showed CIE 1931 color coordinates of (0.667, 0.332), (0.251, 0.299) and (0.333, 0.391) respectively. Significant photoluminescence characteristics of the prepared phosphors indicate that they might serve as potential candidates for blue chip and near‐UV white light‐emitting diode applications. Copyright © 2015 John Wiley & Sons, Ltd.     

Structure and photoluminescent properties of green‐emitting terbium‐doped GdV1−xPxO4 phosphor prepared by solution combustion method

Terbium‐doped gadolinium orthovanadate (GdVO₄:Tb³⁺), orthophosphate monohydrate (GdPO₄·H₂O:Tb³⁺) and orthovanadate–phosphate (GdV,PO₄:Tb³⁺) powder phosphors were synthesized using a solution combustion method. X‐Ray diffraction analysis confirmed the formation of crystalline GdVO₄, GdPO₄·H₂O and GdV,PO₄. Scanning electron microscopy images showed that the powder was composed of an agglomeration of particles of different shapes, ranging from spherical to oval to wire‐like structures. The chemical elements present were confirmed by energy dispersive spectroscopy, and the stretching mode frequencies were determined by Fourier transform infrared spectroscopy. UV–visible spectroscopy spectra showed a strong absorption band with a maximum at 200 nm assigned to the absorption of VO₄^3? and minor excitation bands assigned to f → f transitions of Tb³⁺. Four characteristic emission peaks were observed at 491, 546, 588 and 623 nm, and are attributed to ⁵D₄ → ⁷F_j (j = 6, 5, 4 and 3). The photoluminescent prominent green emission peak (⁵D₄ → ⁷F₅) was centred at 546 nm. The structure and possible mechanism of light emission from GdV_1?xP_xO₄:% Tb³⁺ are discussed. Copyright © 2016 John Wiley & Sons, Ltd.