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A series of RE(OH)SO 4 layered compounds (RE = La–Tb lanthanides) were successfully synthesized via hydrothermal reaction under near-neutral solution pH and the mild temperature of 180 °C for 24 h, and the temperature/pH/time courses of phase/morphology evolution were clarified with RE = Tb for example. The compounds were characterized in detail for crystallite morphology, crystal structure, thermal behavior and vibrational property, and the intrinsic influence of lanthanide contraction was unveiled. Tb(OH)SO 4 was analyzed to be isostructural with its La–Gd analogues (CN = 9 for Tb), instead of the reportedly Dy–Yb ones (CN = 8), and have parameters of a = 4.3806 Å, b = 12.1729 Å, c = 6.7674 Å and β = 106.3967° for its monoclinic unit cell (P 2 1 / n space group). The Eu and Tb compounds exhibited red (λ ex = 395 nm, λ em = 616 nm) and green (λ ex = 369 nm, λ em = 545 nm) emissions, and have fluorescence lifetimes of ∼0.84 and 1.07 ms and chromaticity coordinates of around (0.632, 0.365) and (0.295, 0.481), respectively. [ABSTRACT FROM AUTHOR]

Infrared transparent Ho: Y 2 O 3 -MgO nanocomposite ceramics with a volume ratio of 50:50 (RE 2 O 3 : MgO) were prepared by combining sol-gel powder synthesis and hot-pressing sintering techniques. In order to obtain Ho: Y 2 O 3 -MgO nanocomposite ceramics with fine grain size, dense microstructure and homogeneous phase domains, the effect of sintering temperature and Ho3+ doping concentration were studied. Transmittance and SEM measurement revealed that the grain size of 3 at.% Ho: Y 2 O 3 -MgO ceramic sintered at 1250 °C is 141 nm, and the transmission is up to 85.2% at 5 μm. The detailed spectroscopic investigation of x at.% Ho: Y 2 O 3 -MgO (x = 1, 3, 5, 7, 9, 15) ceramics was performed. The nanocomposites exhibited photoluminescence properties similar to that of Ho: Y 2 O 3 crystals and ceramics. In addition, the thermal conductivity of 3 at.% Ho: Y 2 O 3 -MgO ceramic is 13.04 W/m·K, which is superior to that of Ho:Y 2 O 3 ceramics. The high transmission, excellent thermal conductivity, and outstanding optical characteristics indicated that Ho: Y 2 O 3 -MgO ceramics is a promising material for efficient infrared solid-state laser. [ABSTRACT FROM AUTHOR]

Uniform phosphor mono-spheres have received continuously increasing attention owing to their excellent luminescence properties. Submicron/near micron-sized Lu 2 O 3 :Eu mono-spheres were successfully prepared by a facile and modified homogeneous precipitation technique from corresponding single-source precursor of Lu(OH)CO 3 :Eu⋅ n H 2 O, without the assistance of any dispersants. The sizes of the precursor spheres can be tuned in the range of 56–790 nm via controlling the primary particle nucleation and particle growth in the homogeneous precipitation. After calcination at 1000 °C, the synthesized precursor spheres (165–790 nm) were converted to Lu 2 O 3 :Eu (110–630 nm) without changing their original spherical shape and excellent dispersion. The particle size-dependent photoluminescence properties of Lu 2 O 3 :Eu mono-spheres were investigated in detail. Enhanced photoluminescence intensity, shorter lifetime, higher external quantum efficiency and almost the same CIE chromaticity coordinates were observed for a particle size of 480 nm. Moreover, temperature-dependent photoluminescence spectra indicated the obtained phosphor mono-spheres have good thermal stability. [ABSTRACT FROM AUTHOR]

Spherical silicate phosphor has widespread application in display or lighting industry. By using spherical silica particles as the core, we successfully prepared shell-thickness-controllable core/shell spherical particles, which can then be controllably converted to spherical X 1 -Y 2 SiO 5 :Eu (YSO:Eu) and α-Y 2 Si 2 O 7 :Eu (YPS:Eu) particles upon annealing. Even after 1000–1200 °C annealing, both X 1 -YSO:Eu and α-YPS:Eu particles still had the spherical shape and narrow size distribution. The shell thickness and annealing temperature synergistically controlled the phase evolution upon annealing. Thinner shell of around 30 nm, having extremely high chemical reaction activity, promoted the formation of spherical X 1 -YSO:Eu particles at 1000 °C and α-YPS:Eu particles at 1100 °C. Shell of around 85 nm produced spherical X 1 -YSO:Eu particles at 1100 °C and α-YPS:Eu particles at 1200 °C. Thicker shell also promoted the formation of spherical particles, but these particles usually had the mixed silicate phases. The phase-dependent photoluminescence properties were investigated in detail. Both spherical X 1 -YSO:Eu and α-YPS:Eu phosphors emitted reddish-orange color, with nearly 100% color purity and dominant wavelength of around 601 nm, which would absorb great attention for the application in display or lighting devices. Spherical red-emitting X 1 -Y 2 SiO 5 :Eu and α-Y 2 Si 2 O 7 :Eu phosphors having the nearly 100% color purity were obtained, and the phase transformation sequence was clearly clarified. [Display omitted] [ABSTRACT FROM AUTHOR]

(Tb 0.985 Ce 0.015 ) 3 (Al 1- x Ga x ) 5 O 12 garnet phosphors ( x = 0, 0.1, 0.2, 0.3, and 1.0) were prepared by calcining their coprecipitated precursors in air at 1500 °C, followed by reduction in hydrogen at 1200 °C. Rietveld refinement of the XRD results suggested that the Ga dopant predominantly resides at the octahedral Al site of the garnet lattice. Ga doping led to linearly expanded lattice constant, cell volume and theoretical density of the garnet compound and successively lower intensity and longer average fluorescence lifetime of the ~ 570 nm emission of Ce 3+ . Blue shifted emission and 4f( 2 F 5/2 )→5d 1 (E 2g ) excitation and red shifted 4f( 2 F 5/2 )→5d 2 (E 2g ) excitation were also observed for the Ce 3+ activator at a higher Ga content. The phenomena were interpreted by considering the band structure of the host, distortion of the CeO 8 polyhedron, and centroid shift and field splitting of the Ce 3+ 5d energy levels. [ABSTRACT FROM AUTHOR]

A series of eulytite-type Sr 3 Y 1- x (PO 4 ) 3 : x Eu 3+ ( x = 0–0.13) and Sr 3- y Y(PO 4 ) 3 : y Eu 2+ ( y = 0–0.10) phosphors were successfully synthesized via gel-combustion and subsequent calcination in O 2 and Ar/H 2 atmospheres at 1250 °C, respectively. Detailed crystal structure analysis via Rietveld refinement showed that the phosphors were crystallized in the cubic system (space group I -43 d , No. 220), in which the Eu 3+ and Eu 2+ activators reside at the Y 3+ and Sr 2+ sites, respectively. The trivalent Eu 3+ ions (CN = 6) exhibited typical narrow-band luminescence via intra-4 f 6 transitions, with the red emission at ~ 615 nm being dominant ( 5 D 0 → 7 F 2 transition, FWHM = 15.9 ± 0.2 nm). The divalent Eu 2+ ions (CN = 6 and 9) showed broad-band luminescence ranging from light-blue to blue via 4 f 6 5 d 1 → 4 f 7 transitions (FWHM = 115 ± 2 nm). The optimal Eu 3+ and Eu 2+ concentrations were determined to be 10 at% ( x = 0.10) and 7 at% ( y = 0.07), respectively, and the mechanisms of concentration quenching were discussed. The excitation/emission properties, fluorescence decay kinetics, CIE chromaticity, and particularly the rarely addressed thermal stability of the phosphors were investigated in detail. [ABSTRACT FROM AUTHOR]

(Tb 1 -x Ce x ) 3 Al 5 O 12 yellow phosphors (0≤x≤0.05) were calcined from their coprecipitated carbonate precursors, and the effects of the temperature and atmosphere (air and H 2 ) of calcination on the sequence of phase evolution and the characteristics of the powders were investigated in detail. The activation energy for the crystallite growth during calcination was estimated to be ~39 kJ/mol. The powder calcined at 1000 °C showed good reactivity and was sintered into a ceramic plate of ~97% dense (average grain size: ~1.3 µm) in a H 2 /Ar gas mixture at the relatively low temperature of 1500 °C. The phosphors simultaneously exhibit the 4f 8 →4f 7 5d 1 , 7 F 6 → 5 D 3 and 7 F 6 → 5 D 4 excitations of Tb 3+ and the 4f 1 →5d 1 excitation of Ce 3+ when monitoring the yellow emission of Ce 3+ at 560 nm, suggesting the presence of efficient Tb 3+ →Ce 3+ energy migration. The optimal Ce 3+ content for luminescence was found to be x =0.015 and 0.01 under the direct excitation of Ce 3+ and through Tb 3+ →Ce 3+ energy transfer, respectively, and concentration quenching of luminescence was analyzed to be resulted from exchange interaction. Luminescence features of the phosphors, including excitation, emission, quantum yield, fluorescence lifetime, color coordinates and color temperature, were thoroughly investigated against the processing temperature and Ce 3+ content, with an in-depth discussion on the process of energy transfer among the optically active Tb 3+ and Ce 3+ ions. The materials may find application in blue-light excited white LEDs. [ABSTRACT FROM AUTHOR]