Photoluminescent and cathodoluminescent performances of Tb³⁺in Lu³⁺-stabilized gadolinium aluminate garnet solid-solutions of [(Gd_1−xLu_x)_1−yTb_y]₃Al₅O₁₂

Abstract

A series of [(Gd 1-x Lu x ) 1-y Tb y ] 3 Al 5 O 12 green phosphors have been calcined from their coprecipitated carbonate precursors. Increasing Lu 3+ incorporation was found to significantly simplify the reaction pathway and lower the temperature of garnet formation, and at the same time leads to contracted cell dimension and improved theoretical density. Photoluminescent properties, in terms of excitation, emission, concentration quenching, quantum yield, color coordinates of emission, efficiency of excitation absorption, fluorescence decay, and relative intensity of the 5 D 4 → 5 F 6 / 5 D 4 → 5 F 5 emissions, are thoroughly investigated against the Lu and Tb contents, temperature of phosphor synthesis, and electronegativity of the cations in the host lattice. The best luminescent [(Gd 0.8 Lu 0.2 ) 0.9 Tb 0.1 ]AG combination exhibits photoluminescence very close to (Y 0.9 Tb 0.1 )AG and significantly better than (Lu 0.9 Tb 0.1 )AG.Cathodoluminescence found that the [(Gd 0.8 Lu 0.2 ) 0.9 Tb 0.1 ]AG phosphor is structurally stable in the range of this study, and exhibits successively higher emission brightness by increasing either the acceleration voltage (up to 6 kV) or beam current (up to 55 µA). The high density green phosphor developed in this work may find lighting, display, and scintillation applications. 5 coprecipitation, phase evolution, structure characterization, and photoluminescent and cathodoluminescent properties of the [(Gd 1-x Lu x ) 1-y Tb y ] 3 AG green phosphors. ExperimentalThe rare earth sources for powder synthesis are RE 2 O 3 (RE=Gd, Lu, Y) and Tb 4 O 7 , all 99.99% pure products from Huizhou Ruier Rare Chemical Hi-Tech Co. Ltd (Huizhou, China).The aluminum source is >99% pure alum (NH 4 Al(SO 4 ) 2 ·12H 2 O) from Zhenxin Chemical Reagent Factory (Shanghai, China). All the other reagents are of analytical grade products from Shenyang Chemical Reagent Factory (Shenyang, China). Nitrate solution of the rare-earth was prepared by dissolving the corresponding oxide in concentrated HNO 3 , followed by evaporation to dryness at 100 o C to remove superfluous HNO 3 and then a final dilution with distilled water to 0.3 mol/L. The precursor for phosphor oxide was made via carbonate coprecipitation with ammonium hydrogen bicarbonate (NH 4 HCO 3 , AHC) as the precipitant, which has the advantages of stoichiometric precipitation of the constituent cations and low aggregation of the final oxide powders. 10,16,17 Aqueous salt solutions for precipitation were made from the nitrate solutions and alum according to the formula of [(Gd 1-x Lu x ) 1-y Tb y ] 3 Al 5 O 12 (x=0.1-0.5, y=0-0.15).Carbonate precursors were precipitated by dropwise adding 200 mL of a 0.125 mol/L (for Al 3+ ) mixed solution into 320 mL of a 1.5 mol/L AHC solution under mild stirring at room temperature. In all the cases, the total concentration of Gd 3+ , Lu 3+ and Tb 3+ was kept constant at 0.075 mol/L so that the (Gd+Lu+Tb):Al atomic ratio would be the 3:5 of the garnet formula. The precipitate was homogenized for 30 min after the...

Production and optical properties of Ce3+‐activated and Lu3+‐stabilized transparent gadolinium aluminate garnet ceramics

“…The fine (Gd,Lu) 3 Al 5 O 12 :Ce phosphor powder has a much higher specific surface area than the ceramic bulk, resulting in a relatively short effective fluorescence lifetime. The fluorescence lifetimes of the (Gd,Lu) 3 Al 5 O 12 :Ce phosphor powder and transparent ceramic determined in this work also approximate the reported values of the fluorescence lifetimes of the YAG:Ce and LuAG:Ce phosphor powders and transparent ceramics …”

“…Figure exhibits the responses of the (Gd,Lu) 3 Al 5 O 12 :Ce phosphor powder and transparent ceramic to 457 nm excitation using a solid BaSO 4 white standard as a reference material. The external quantum efficiencies (ɛ ex ) and the internal quantum efficiencies (ɛ in ) of the two samples were automatically deduced from Equations and , respectively, via the software in the spectrophotometer:where P(λ)/hν , R(λ)/hν , and E(λ)/hν are the numbers of photons in the emission, reflectance, and excitation spectra of the samples, respectively.…”

“…The percentage of excitation absorption ( η ) can be calculated from the ratio of ɛ ex to ɛ in expressed as Equation ():…”

“…Li et al found that a small level of Lu 3+ dopant could effectively suppress the thermal decomposition of GAG and significantly increase its X‐ray stopping ability and its optical bandgap . Using this novel (Gd,Lu)AG matrix, they developed a series of (Gd,Lu)AG:Ln (Ln = Eu, Ce, Tb, etc) phosphor powders …”

“…11 Using this novel (Gd,Lu)AG matrix, they developed a series of (Gd,Lu)AG:Ln (Ln = Eu, Ce, Tb, etc) phosphor powders. 16,18,19 To the best of our knowledge, there has been few reports on fabrication of (Gd,Lu)AG-based transparent ceramic materials until now. In this work, transparent (Gd 0.64 Lu 0.35 Ce 0.01 ) 3 Al 5 O 12 ceramics with an in-line transmittance around 70% at 580 nm were first successfully fabricated from their garnet phosphor powders prepared via combined co-precipitation and thermolysis.…”