Nd3+‐Yb3+/Nd3+‐Yb3+‐Li+ co‐doped Gd2O3 phosphors for up and down conversion luminescence

Frequency up‐conversion (UC) emission from the Nd³⁺‐Yb³⁺/Nd³⁺‐Yb³⁺‐Li⁺ co‐doped gadolinium oxide (Gd₂O₃) phosphors prepared by the solution combustion technique in the visible range have been studied by using 980 nm near infrared (NIR) laser diode excitation. The crystalline structure and formation of the cubic phase has been confirmed with the help of X‐ray diffraction (XRD) studies. XRD peak shifts have been found towards the lower diffraction angle side in the case of the Nd³⁺‐Yb³⁺‐Li⁺ co‐doped phosphors. Surface morphology and particle size information have been observed by using field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) analysis. Down‐conversion emission study under 351 nm excitation in the visible region for the Nd³⁺‐Yb³⁺/Nd³⁺‐Yb³⁺‐Li⁺ co‐doped phosphors has been performed. The UC emission bands lying in the green and red region arising from the Nd³⁺ ions have been enhanced by ~260 times, ~113 times due to incorporation of Li⁺ ions in the Nd³⁺‐Yb³⁺ co‐doped phosphors. Photometric characterization has been done for the Nd³⁺‐Yb³⁺/Nd³⁺‐Yb³⁺‐Li⁺ co‐doped phosphors. The present study suggests the capability of the synthesized phosphors in near‐infrared (NIR) to visible upconverter and luminescent device applications.     

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.     

Spectral investigations on Eu3+,Sm3+‐doped and Sm3+/Eu3+ co‐doped potassium‐fluoro‐phosphate glass emitting intense orange‐red for lighting applications

Potassium fluoro‐phosphate (KFP) glass singly doped with different concentrations of europium (Eu³⁺) or samarium (Sm³⁺) or co‐doped (Sm³⁺/Eu³⁺) was prepared, and their luminescence spectra were investigated. The phase composition of the product was verified by X‐ray diffraction analysis. Optical transition properties of Eu³⁺ in the studied potassium phosphate glass were evaluated in the framework of the Judd–Ofelt theory. The radiative transition rates (A_R), fluorescence branching ratios (β), stimulated emission cross‐sections (σ_e) and lifetimes (τ_exp) for certain transitions or levels were evaluated. Red emission of Eu³⁺ was exhibited mainly by the ⁵D₀→⁷F₂ transition located at 612 nm. Concentration quenching and energy transfer were observed from fluorescence spectra and decay curves, respectively. It was found that the lifetimes of the ⁵D₀ level increased with increase in concentration and then decreased. By co‐doping with Sm³⁺, energy transfer from Sm³⁺ to Eu³⁺ occurred and contributed to the enhancement in emission intensity. Intense orange‐red light emission was obtained upon sensitizing with Sm³⁺ in KFP glass. This approach shows significant promise for use in reddish‐orange lighting applications. The optimized properties of the Sm³⁺/Eu³⁺ co‐doped potassium phosphate glass might be promising for optical materials.     

Tunable emission,energy transfer and charge compensation in SrMoO4:Sm3+,Tb3+,Na+ phosphor

A series of SrMoO₄:Sm³⁺,Tb³⁺,Na⁺ phosphors was synthesized using a high‐temperature solid‐state reaction method in air. On excitation at 290 nm, SrMoO₄:Sm³⁺,Tb³⁺ phosphor emitted light that varied systematically from green to reddish‐orange on changing the Sm³⁺ and Tb³⁺ ion concentrations. The emission intensities of SrMoO₄:Sm³⁺ and SrMoO₄:Sm³⁺,Tb³⁺ phosphors were increased two to four times due to charge compensation when Na⁺ was added as a charge compensator. The luminescence mechanism and energy transfer could be explained using energy‐level diagrams of the MoO₄^2– group, Sm³⁺ and Tb³⁺ ions. SrMoO₄:Sm³⁺,Tb³⁺,Na⁺ could be used as reddish‐orange phosphor in white light‐emitting diodes (LEDs) based on an ~ 405 nm near‐UV LED chip. This research is helpful in adjusting and improving the luminescence properties of other phosphors. Copyright © 2015 John Wiley & Sons, Ltd.     

An efficient orange–red‐emitting LiNa3P2O7:Sm3+ pyrophosphate: Structural and optical analysis for solid‐state lighting

A trivalent rare‐earth ion (Sm³⁺)‐doped LiNa₃P₂O₇ (LNPO) phosphor was synthesized using a conventional high‐temperature solid‐state reaction route. A predominant orthorhombic phase of LNPO was observed in all X‐ray diffraction patterns. The surface states of the LNPO:Sm phosphor were confirmed by X‐ray photoelectron spectroscopy. Under 401 nm excitation, the Sm‐doped LNPO phosphors showed sharp emission peaks at 563, 600 and 647 nm that are related to the f–f transition of Sm³⁺ ions. The optimum concentration of Sm³⁺ (9 mol%) produced Commission Internationale de l'Eclairage chromaticity coordinates, color rendering index and correlated color temperature of (0.564, 0.434), 42 and 1843 K, respectively.     

Synthesis and photoluminescence properties of Sm3+‐doped YAl3(BO3)4 phosphor

A near ultraviolet excitable phosphor based on Sm³⁺‐doped YAl₃(BO₃)₄ has been synthesized by modified solid‐state reaction at 1000°C. The phase purity and photoluminescence (PL) behavior of the phosphor are studied in detail using the powder X‐ray diffraction technique and PL measurements. X‐ray diffraction reveals that the phase purity of YAl₃(BO₃)₄ critically depends upon the boric acid concentration. The phosphor has strong excitation at 406 nm in the near ultraviolet region (350–420 nm) and its emission peaks were monitored at 564, 599 and 643 nm. Further, detailed PL analysis demonstrates that the substitution of Sm³⁺ ions at sites of Y³⁺ and Al³⁺ ions enhances the PL efficiency of the phosphor appreciably. First, the PL efficiency of YAl₃(BO₃)₄:Sm³⁺ was compared with commercial (Y,Gd)BO₃:Eu³⁺ red phosphor. The Fourier transform infrared study provides essential information regarding the change in metal–oxygen bond vibrations of the phosphor. The morphology of the phosphor was investigated through scanning electron microscopy, which reveals that the phosphor possessed distorted spherical and rectangular shapes with average grain sizes in the range 0.5–1 µm. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis and photoluminescence characteristics of Sm3+‐doped Bi4Si3O12 red‐emitting phosphor

A series of novel red‐emitting Sm³⁺‐doped bismuth silicate phosphors, Bi₄Si₃O₁₂:xSm³⁺ (0.01 ≤ x ≤ 0.06), were prepared via the sol–gel route. The phase of the synthesized samples calcinated at 800 °C is isostructural with Bi₄Si₃O₁₂ according to X‐ray diffraction results. Under excitation with 405 nm light, some typical peaks of Sm³⁺ ions centered at 566, 609, 655 and 715 nm are found in the emission spectra of the Sm³⁺‐doped Bi₄Si₃O₁₂ phosphors. The strongest peak located at 609 nm is due to ⁴G_5/2–⁶H_7/2 transition of Sm³⁺. The luminescence intensity reaches its maximum value when the Sm³⁺ ion content is 4 mol%. The results suggest that Bi₄Si₃O₁₂:Sm³⁺ may be a potential red phosphor for white light‐emitting diodes. Copyright © 2016 John Wiley & Sons, Ltd.     

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.     

Luminescent properties of Ca3SiO4Cl2 co‐doped with Ce3+ and Eu2+ for near‐ultraviolet light‐emitting diodes

Ca₃SiO₄Cl₂ co‐doped with Ce³⁺,Eu²⁺ was prepared by high temperature reaction. The structure, luminescent properties and the energy transfer process of Ca₃SiO₄Cl₂: Ce³⁺,Eu²⁺ were investigated. Eu²⁺ ions can give enhanced green emission through Ce³⁺ → Eu²⁺ energy transfer in these phosphors. The green phosphor Ca_2.9775SiO₄Cl₂:0.0045Ce³⁺,0.018Eu²⁺ showed intense green emission with broader excitation in the near‐ultraviolet light range. A green light‐emitting diode (LED) based on this phosphor was made, and bright green light from this green LED could be observed by the naked eye under 20 mA current excitation. Hence it is considered to be a good candidate for the green component of a three‐band white LED. Copyright © 2015 John Wiley & Sons, Ltd.     

Luminescence and energy‐transfer properties of color‐tunable Ca2Mg0.25Al1.5Si1.25O7:Ce3+/Eu2+/Tb3+ phosphors for ultraviolet light‐emitting diodes

A series of Ca₂Mg_0.25Al_1.5Si_1.25O₇:Ce³⁺/Eu²⁺/Tb³⁺ phosphors was been prepared via a conventional high temperature solid‐state reaction and their luminescence properties were studied. The emission spectra of Ca₂Mg_0.25Al_1.5Si_1.25O₇:Ce³⁺,Eu²⁺ and Ca₂Mg_0.25Al_1.5Si_1.25O₇:Ce³⁺,Tb³⁺ phosphors show not only a band due to Ce³⁺ ions (409 nm) but also as a band due to Eu²⁺ (520 nm) and Tb³⁺ (542 nm) ions. More importantly, the effective energy transfer from Ce³⁺ to Eu²⁺ and Tb³⁺ ions was confirmed and investigated by emission/excitation spectra and luminescent decay behaviors. Furthermore, the energy level scheme and energy transfer mechanism were investigated and were demonstrated to be of resonant type via dipole–dipole (Ce³⁺ to Eu²⁺) and dipole–quadrupole (Ce³⁺ to Tb³⁺) reactions, respectively. Under excitation at 350 nm, the emitting color could be changed from blue to green by adjusting the relative doping concentration of Ce³⁺ and Eu²⁺ ions as well as Ce³⁺ and Tb³⁺ ions. The above results indicate that Ca₂Mg_0.25Al_1.5Si_1.25O₇:Ce³⁺,Eu²⁺/Tb³⁺ are promising single‐phase blue‐to‐green phosphors for application in phosphor conversion white‐light‐emitting diodes. Copyright © 2015 John Wiley & Sons, Ltd.     

Structural and luminescence properties of Sm3+‐doped bismuth phosphate glass for orange‐red photonic applications

In the present study, the effect of bismuth oxide (Bi₂O₃) content on the structural and optical properties of 0.5Sm³⁺‐doped phosphate glass and the effect of concentration on structural and optical properties of Sm³⁺‐doped bismuth phosphate (BiP) glass were studied. Structural characterization was accomplished using X‐ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy and ³¹P nuclear magnetic resonance (NMR) spectroscopy. Optical properties were studied using absorption, photoluminescence and decay measurements. Using optical absorption spectra, Judd–Ofelt parameters were derived to determine the local structure and bonding in the vicinity of Sm³⁺ ions. The emission spectra of Sm³⁺‐doped BiP glass showed two intense emission bands, ⁴G_5/2→⁶H_7/2 (orange) and ⁴G_5/2→⁶H_9/2 (red) for which the stimulated emission cross‐sections (σ_e) and branching ratios (β) were found to be higher. The quantum efficiencies were also calculated from decay measurements recorded for the ⁴G_5/2 level of Sm³⁺ ions. The suitable combination of Bi₂O₃ (10 mol%) and Sm³⁺ (0.5 mol%) ions in these glasses acted as an efficient lasing material and might be suitable for the development of visible orange‐red photonic materials.     

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.     

Thermoluminescence and photoluminescence studies on γ‐ray‐irradiated Ce3+,Tb3+‐doped potassium chloride single crystals

Single crystals of KCl doped with Ce³⁺,Tb³⁺ were grown using the Bridgeman–Stockbarger technique. Thermoluminescence (TL), optical absorption, photoluminescence (PL), photo‐stimulated luminescence (PSL), and thermal‐stimulated luminescence (TSL) properties were studied after γ‐ray irradiation at room temperature. The glow curve of the γ‐ray‐irradiated crystal exhibits three peaks at 420, 470 and 525 K. F‐Light bleaching (560 nm) leads to a drastic change in the TL glow curve. The optical absorption measurements indicate that F‐ and V‐centres are formed in the crystal during γ‐ray irradiation. It was attempted to incorporate a broad band of cerium activator into the narrow band of terbium in the KCl host without a reduction in the emission intensity. Cerium co‐doped KCl:Tb crystals showed broad band emission due to the d–f transition of cerium and a reduction in the intensity of the emission peak due to ⁵D₃–⁷F_j (j = 3, 4) transition of terbium, when excited at 330 nm. These results support that energy transfer occurs from cerium to terbium in the KCl host. Co‐doping Ce³⁺ ions greatly intensified the excitation peak at 339 nm for the emission at 400 nm of Tb³⁺. The emission due to Tb³⁺ ions was confirmed by PSL and TSL spectra. 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.     

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.     

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.     

Synthesis and characterization of blue long‐lasting BaCa2Al8O15:Eu2+, Dy3+ phosphor

We have synthesized and characterized a new BaCa₂Al₈O₁₅:Eu²⁺,Dy³⁺ phosphor prepared by the combustion method. X‐ray diffraction, thermoluminescence, scanning electron microscope, time decay and optical spectral analysis photoluminescence excitation, emission spectra were used to characterize the phosphors. Broadband ultraviolet excited luminescence of the BaCa₂Al₈O₁₅:Eu²⁺,Dy³⁺ was observed in the blue region (λ_max = 435 nm) due to transitions from the 4f⁶5d¹ to the 4f⁷ configuration of the Eu²⁺ ion. Scanning electron microscopy has been used for exploring the morphological properties of the prepared phosphors. The BaCa₂Al₈O₁₅:Eu²⁺ phosphor has a blue afterglow when Dy³⁺ ions were co‐doped. The thermoluminescence spectra show that the Dy³⁺ ion induces a proper trap in the phosphor with a depth of 0.67 eV and results in a long afterglow phosphorescence. Copyright © 2013 John Wiley & Sons, Ltd.     

Luminescent properties of single‐phase Ba2‐x‐1.5y‐1.5zP2O7:xEu2+,yCe3+, zTb3+ phosphors for white light‐emitting diode

A series of Ba₂P₂O₇:xEu²⁺,yCe³⁺,zTb³⁺ phosphors was synthesized via a co‐precipitation method, then their crystal structure, quantum efficiency and luminescent properties were analyzed by XRD and FL, respectively. The results showed that these phosphors not only presented the excitation characteristics of Ba₂P₂O₇:xEu²⁺,zTb³⁺, but also exhibited that of the Ba₂P₂O₇:yCe³⁺,zTb³⁺ phosphor. Meanwhile, the tri‐doped phosphor showed a stronger absorption around 320 nm in contrast with the Eu²⁺/Ce³⁺:Tb³⁺ co‐doped phosphor. Not only can energy transfer from Ce³⁺→Eu²⁺ be observed; the energy transfer mechanism from Eu²⁺ to Tb³⁺ is discussed in the tri‐doped system. Ce³⁺ affects the luminescence properties of Ba₂P₂O₇:xEu²⁺,yCe³⁺,zTb³⁺ phosphors just as the sensitizer whereas Eu²⁺ is considered both as the sensitizer and the activator. The chromaticity coordinates of tri‐doped phosphors excited at 320 nm stayed steadily in the bluish‐white light region,and the emitted color and color temperature (CCT) of these phosphors could be tuned by adjusting the relative contents of Eu²⁺, Ce³⁺ and Tb³⁺. Hence, the single phase Ba₂P₂O₇:xEu²⁺,yCe³⁺,zTb³⁺ phosphors may be considered as potential candidates for white light‐emitting diodes.     

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).     

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.