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Y 2 O 3 :Yb3+, Er3+, Eu3+ phosphors with different Yb3+, Er3+ and Eu3+ doping concentrations were prepared by sol-gel method using glycine as a chelating agent. The effect of Yb3+/Er3+/Eu3+ doping concentrations on the upconversion and near-infrared spectral performances of the synthesized phosphors were investigated. The XRD analysis shows that the samples calcined at 1000 °C for 2 h are well-crystallized and show a pure cubic Y 2 O 3 phase. Upon excitation of 980 nm excitation source, the emission intensity of green/red upconversion and 1.54 μm near-infrared emission of the samples can be adjusted with the variation of Eu3+ doping concentrations. The samples also display a color-tunable upconversion emission with the variation of Eu3+ doping concentration and the excitation power of 980 nm laser diode. In addition, the energy transfer mechanism among Yb3+, Er3+ and Eu3+ in upconversion and 1.54 μm emission processes are also discussed. • Sol-gel synthesis of Y 2 O 3 :Yb3+, Er3+, Eu3+ phosphors. • 980 nm LD excited color-tunable upconversion luminescence. • Eu3+ doping can apparently enhance the 1.54 μm NIR emission intensity of the samples. • Applications in optical communications, eye-safe laser, display devices, solar cells. [ABSTRACT FROM AUTHOR]

Nanosized Ce 3+ and Tb 3+ co-doped LaPO 4 phosphors were synthesized by a mixed co-precipitation method using oxalic acid (H 2 C 2 O 4 ·2H 2 O) and ammonium dibasic phosphate ((NH 4 ) 2 HPO 4 ) as the precipitants. The morphology, crystal structure and photoluminescence properties of the synthesized LaPO 4 :Ce 3+ ,Tb 3+ phosphors were investigated by thermo-gravimetry and differential scanning colorimetry, X-ray diffraction, scanning electron microscope, and photoluminescence emission spectra methods. The results showed that the pure phase of lanthanum orthophosphate can be formed with a lower calcining temperature compared to that of the traditional solid-state reaction method. LaPO 4 phosphors doped with 20 mol% Tb 3+ and 40 mol% Ce 3+ , which were calcined at 900 °C for 1 h, reached the maximum emission intensity under 265 nm excitation. The most prominent emission was at 543 nm, which corresponded to the 5 D 4 → 7 F 5 transition of Tb 3+ ions. [ABSTRACT FROM AUTHOR]

Abstract: Trivalent neodymium ion doped yttria (Nd3+:Y2O3) nanopowders were synthesized by using a glycine combustion method. The characteristics of the Nd3+:Y2O3 nanopowders with different calcination temperatures and Nd3+ ion doping concentrations were analyzed to determine the optimum synthesis conditions of the samples. Thermo-gravimetry and differential scanning colorimetry (TG/DSC), XRD and FTIR analysis showed that the novel glycine-gel microwave combustion method can provide an effective reaction to form yttria nanopowders. The peak positions of the emission spectra of Nd3+ ion in yttria host did not differ with the neodymium ion concentration or the calcination temperatures, whereas the luminescence intensities were heavily dependent on the ion concentration and calcination temperatures. [Copyright &y& Elsevier]

Abstract: Highly transparent Er3+/Yb3+ co-doped yttria ceramics were fabricated by a solid-state reaction method using high purity Y2O3, Er2O3 and Yb2O3 powders as starting materials and La2O3 as an additive. The microstructure evolution and optical properties of the ceramics were investigated. Fully dense Y2O3: Er3+, Yb3+ ceramics with mean grain size of about 60 μm were obtained by vacuum sintering at 1800 °C for 10 h. The highest transmittance of the ceramic sample is more than 75% in the range from 500 to 3000 nm. Under the 980 nm laser diode excitation, the ceramic sample exhibits intense up-conversion luminescence, which is centered at 561 and 662 nm respectively. [Copyright &y& Elsevier]

Abstract: Nanosized ytterbium doped yttria powders were prepared by citrate-gel combustion techniques. As-synthesized precursor and calcined powders were characterized for their crystalline structure, particle size and morphologies. Nanocrystalline Yb3+:Y2O3 powders with pure cubic yttria crystal structure were obtained by calcination of as-prepared precursors at 1100°C for 3h. Powders obtained were well dispersed with an average particle size of 60nm. By using the obtained powders, nearly full dense Yb3+:Y2O3 ceramics were produced by vacuum sintering at 1800°C for 12h. The emission spectrum of the sintered ceramics under the excitation wavelength of 905nm illustrates that there are three fluorescence peaks locating at 976nm, 1030nm and 1075nm respectively, all corresponding to the 2 F 5/2 → 2 F 7/2 transitions of ytterbium ion. [Copyright &y& Elsevier]

Abstract: Ytterbium-doped yttria (Yb3+:Y2O3) nanopowders for transparent ceramics were synthesized by using a carbonate-precipitation method. The characteristics of precursor and powders calcined at different temperatures were investigated. The pure yttria phase can form through calcining at 700°C. The Yb3+:Y2O3 nanopowders calcined at 1100°C were well dispersed with a spherical morphology, and had a narrow particle size distribution with a mean particle size of about 70nm. By using 1100°C-calcined powders, nearly full dense Yb3+:Y2O3 ceramics were fabricated at 1750°C for 8h without any additives under vacuum conditions. The fluorescence spectrum of the sintered ceramics illustrates that there are two emission peaks locating at 1028 and 1071nm respectively, all corresponding to the 2 F 5/2 → 2 F 7/2 transitions of Yb3+ ion. Homogeneous Yb3+:Y2O3 nanopowders synthesized by carbonate-precipitation method are suitable for the fabrication of IR-transparent ceramics. [ABSTRACT FROM AUTHOR]

• Solid-state reaction synthesis of Na(Y, Gd)F 4 :Yb3+, Er3+ phosphors. • 980/1550 nm laser excited color-tunable upconversion luminescence. • Gd3+ ion doping can obviously enhance the UC luminescence intensity of the samples. • Applications in bio-science and PV solar cells. A series of Na(Y, Gd)F 4 :Yb3+,Er3+ phosphor samples co-doped with different concentrations of Gd3+, Yb3+ and Er3+ ions were synthesized at 550 °C for 2 h by a solid-state reaction method. The crystal structure and upconversion (UC) luminescence properties of the samples upon 980/1550 nm wavelength excitation were characterized by XRD and emission spectral analysis methods. The XRD analysis showed that the synthesized samples were all pure hexagonal β-NaYF 4 phase. The doping of Gd3+ ions into β-NaYF 4 solid solution matrix can obviously enhance the UC luminescence intensity of the NaYF 4 : Yb3+, Er3+ samples both upon 980 and 1550 nm laser diode excitation. Moreover, the UC emission of the 1550 nm excited Na(Y, Gd)F 4 :Yb3+,Er3+ samples had a better color tunability than that of the UC emission of the 980 nm excited samples. Meanwhile, based on the experimental results, the UC luminescence mechanisms of the sample upon 980 and 1550 nm excitation were also discussed. [ABSTRACT FROM AUTHOR]

Highly transparent Er3+, Yb3+:Y 2 O 3 ceramics were fabricated by pressureless vacuum sintering method using La 2 O 3 and ZrO 2 as compound sintering additives. The microstructure, optical transmittance, upconversion and near-infrared spectral properties of the ceramics were investigated by X-ray diffraction, scanning electron microscopy, energy-dispersive spectrometry and spectroscopic analysis methods. The sintered ceramics displayed a pure cubic Y 2 O 3 phase structure and a nearly pore-free microstructure with homogeneous grain morphology and grain-size distribution. The highest transmittance of Er3+, Yb3+:Y 2 O 3 ceramics sintered at 1800 °C for 14 h with 9 at% of La 2 O 3 and 3 at% of ZrO 2 as compound additives was more than 82% in the range of 380–3000 nm. Under 980 nm wavelength excitation, the ceramics exhibited intense blue, green and red upconversion emission, and broad-bandwidth near-infrared emission centered at 1536 nm, which gives it the potential to act as a high-performance solid-state 1.54 μm near-infrared and upconversion laser gain media. • Pressureless vacuum sintering of highly transparent Er3+, Yb3+:Y 2 O 3 ceramics. • Using La 2 O 3 and ZrO 2 as compound sintering additives. • The highest transmittance of more than 82% was achieved in the range of 380–3000 nm. • The ceramics demonstrated intense blue, green and red upconversion emission. • The ceramics showed broad-bandwidth near-infrared emission centered at 1536 nm. [ABSTRACT FROM AUTHOR]

Abstract: Mg0.20Zn0.80O films have been prepared on quartz substrates by using radio frequency (RF) magnetron sputtering, and metal–semiconductor–metal (MSM) structured photodetectors have been fabricated on the Mg0.20Zn0.80O films employing interdigital Au as metal contacts. We have investigated the effects of electrode spacings on the properties of Mg0.20Zn0.80O MSM photodetectors. It was shown that both of dark currents and responsivities of the devices will decrease with the increasing electrode spacing at the same bias. It was thought that the resistance and the depletion region between the electrodes play important roles in the devices, and the physical mechanism can be explained by a straightforward qualitative model. [ABSTRACT FROM AUTHOR]