Crystals
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2018
·Vol. 8
·期 3
·113
·
IF 2.144
Hui Wang,Qin Li,Chaoyue Wang,Huan He,Jianding Yu,Jiayue Xu
High-quality Ta-doped La2Ti2O7(Ta-LTO) single crystal of about 40 mm in length and 5 mm in diameter was successfully prepared by the optical floating zone method. An X-ray rocking curve reveals that the crystal of LTO has excellent crystalline quality. As-grown crystals were transparent after annealing in air and the transmittance is up to 76% in the visible and near-infrared region. X-ray diffraction showed that this compound possessed a monoclinic structure with P21space group. The dielectric properties were investigated as functions of temperature (0~300 °C) and frequency (102Hz~105Hz). Dielectric spectra indicated an increase in the room-temperature dielectric constant accompanied by a drop in the loss tangent as a result of the Ta doping. One relaxation was observed in the spectra of electric modulus, which was ascribed to be related to the oxygen vacancy. The dielectric relaxation with activation energy of 1.16 eV is found to be the polaron hopping caused by the oxygen vacancies.Keywords:Ta-LTO single crystal;floating zone method;dielectric properties;oxygen vacancy
研究领域:
材料科学
·
物理学
✓ 已验证
产品关联
DOI
高影响因子
CERAMICS INTERNATIONAL
·
2019
·
IF 3.45
Shoulei Xu,Xiaojun Tan,Fenhong Liu,Lei Zhang,Yuyang Huang,Bernard Albert Goodman,Wen Deng
Single crystals of yttria stabilized zirconia (YSZ) doped with different thulia (Tm 2 O 3 ) contents (0.2–3.0 mol%) (abbreviated to Tm 2 O 3 : YSZ) were grown by the optical floating zone method. The crystals were transparent and inclusion free. These samples were then analyzed by X-ray diffraction (XRD), thermogravimetric-differential thermal analysis (TG-DSC), and Raman spectroscopy , and their optical properties were determined with Ultraviolet–visible (UV–Vis) and Photoluminescence spectroscopy (PL). The Tm 2 O 3 : YSZ single crystals were in the cubic phase, and the lattice parameters first increased and then decreased with increasing Tm 2 O 3 content. The absorption spectra showed four peaks at around 356 nm ( 3 H 6 → 1 D 2 ), 460.5 nm ( 3 H 6 → 1 G 4 ), 678.5 nm ( 3 H 6 → 3 F 2,3 ) and 784 nm ( 3 H 6 → 3 H 4 ) in the visible region, and the optical bandgap energy increased with increasing Tm 2 O 3 content, as a result of the Moss-Burstein effect. Measurements of PL spectra indicated a strong blue emission peak at 458 nm ( 1 D 2 → 3 F 4 ), and three weak emission peaks at 487 nm ( 1 G 4 → 3 H 6 ), 497 nm ( 1 D 2 → 3 H 5 ), and 656.5 nm ( 1 G 4 → 3 F 4 ) when the crystals were excited by light with a wavelength of 356 nm. The intensities of the emission peaks were strongly affected by the Tm 2 O 3 content of the YSZ single crystals; the intensity increased with Tm 2 O 3 content at low doping levels, reached the maximum at 0.5 mol% Tm 2 O 3 , then decreased with further increase in Tm 2 O 3 content due to the concentration quenching effect. Additionally, the color changed from blue to cyan as the Tm 2 O 3 content was increased. Overall, this work demonstrates that the cubic YSZ single crystal is a suitable host material for solid state luminescence.
研究领域:
材料科学
·
光学
✓ 已验证
产品关联
DOI
高影响因子
Crystals
·
2021
·Vol. 11
·期 11
·1328
·
IF 2.589
Daini Wang,Wenxia Wu,Xiaojun Tan,Bernard A. Goodman,Shoulei Xu,Wen Deng
As a development on previous research on single crystals of Pr3+-doped yttria-stabilized zirconia (YSZ), we report here the preparation and optical properties of Yb/Pr co-doped YSZ single crystals with different Yb2O3concentrations. Results from X-ray diffraction (XRD) and Raman spectroscopy indicated that all of the crystal samples had a cubic phase structure, and transmission was ≥88% in the 550–780 nm range. Photoluminescence (PL) under excitation with a 980 nm laser showed upconversion emission, and several peaks were observed centered on 448 nm, 508 nm, 525 nm, 542 nm, 617 nm and 656 nm. The effects of excited state absorption (ESA), energy transfer upconversion (ETU), cross relaxation (CR), and cooperative energy transfer (CET) on the upconversion luminescence and energy transition mechanism in YSZ crystals were further studied. The fluorescence lifetime of the3P0→3H5transition at 542 nm reached 207 μs, which shows that the samples are of potential use for laser and fluorescence output.Keywords:optical floating zone method;yttria-stabilized zirconia (YSZ) single crystal;Pr/Yb co-doped;upconversion luminescence
研究领域:
材料科学
·
光学
✓ 已验证
产品关联
DOI
高影响因子
OPTICAL MATERIALS
·
2019
·
IF 2.687
Fenhong Liu,Bernard A. Goodman,Xiaojun Tan,Xiangyu Wang,Danxin Chen,Wen Deng
Rubies (Cr: Al 2 O 3 single crystals) with 0.025–0.4 mol% Cr 2 O 3 were prepared by the optical floating zone method, and characterized by X-ray diffraction (XRD), electron paramagnetic resonance (EPR) spectroscopy, optical transmission and photoluminescence (PL). Crystals were free of inclusions and cracks, and had high transmittance in the visible region. In addition to the well-known signals from Cr 3+ in the α-Al 2 O 3 structure, the EPR spectra indicated the presence of very weak signals, which may correspond to paramagnetic centres associated with an oxygen vacancy , and an electron-loss oxygen centre, O − . The concentration of these paramagnetic centres was at a minimum for Cr 2 O 3 concentration of 0.15 mol%, and additional Cr 3+ -derived peaks were also observed with Cr 2 O 3 concentrations >0.15 mol%. The PL spectra also varied with Cr 2 O 3 concentrations; the emission intensities of the PL spectra increased with Cr 2 O 3 concentration for concentrations ≤0.15 mol%, then decreased with the further increases in Cr 2 O 3 . Thus the maximum luminescence emission intensity and the minimum concentration of paramagnetic structural defects were observed with 0.15 mol % Cr 2 O 3 , and the presence of additional interactions involving Cr 3+ ions may contribute to the partial quenching of the luminescence at higher Cr 3+ concentrations. Overall, the optical floating zone method represents an effective and economic approach to the preparation of high quality rubies, and their optimum optical properties were observed with Cr 2 O 3 concentrations of 0.15 mol%.
研究领域:
材料科学
·
光学
✓ 已验证
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DOI
高影响因子
CRYSTENGCOMM
·
2022
·Vol. 24
·期 43
·7669-7676
·
IF 3.756
Shengdi Ta,Huiting Zhang,Wenxia Wu,Yazhao Wang,Peng Zhang,Zeyu Cheng,Shoulei Xu,Bernard Albert Goodman,Wen Deng
The synthesis, structure, and optical properties are reported for a series of yttria-stabilized zirconia crystals in which some Y3+ was replaced by Eu3+. These crystals were grown by the optical floating zone (OFZ) method and were transparent without inclusions, cracks, or bubbles. They were all exclusively in the cubic phase, whereas the corresponding ceramic samples had a mixture of monoclinic and cubic phases. Absorption spectra showed a charge transfer band at 268 nm and a series of narrow peaks in the range 308–540 nm from Eu3+ f–f transitions. The crystals were efficiently excited at 393 nm, and exhibited excellent orange-red photoluminescence (PL) centred at 610 nm, from the 5D0 → 7F1 transition. The maximum PL intensity was observed with crystals prepared with 2.00 mol% Eu2O3, and compared with other rare earth ions; Eu3+-doped ZrO2–Y2O3 single crystals have a high concentration quenching threshold. The critical distance for Eu3+ ions was calculated as 11.8 Å, which indicates that multipole–multipole interactions dominate the non-radiative energy transfer between Eu3+ ions. Finally, the chromaticity coordinates (CIE) for all the samples were similar, and those for the (ZrO2)92(Y2O3)6(Eu2O3)2 crystal were (x = 0.6339, y = 0.3657) with a colour purity >98%.
研究领域:
材料科学
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光学
·
晶体生长
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发光材料
·
固体物理
✓ 已验证
DOI
高影响因子
JOURNAL OF LUMINESCENCE
·
2019
·
IF 2.961
Xiangyu Wang,Xiaojun Tan,Shoulei Xu,Fenhong Liu,Bernard A. Goodman,Wen Deng
High-quality yttria-stabilized zirconia (YSZ) single crystals doped with different concentrations of Er 2 O 3 were grown by the optical floating zone method . The cubic phase of ZrO 2 was retained when Er 3+ partially replaced Y 3+ in the YSZ matrix. Up-conversion luminescence was observed when the crystals were excited by a 980 nm laser diode . The optical power curve was obtained by plotting the up-conversion luminescence intensity against the laser power, and both the green and red light up-conversion were shown to involve two photons. Seven characteristic visible and three infrared absorption peaks were observed in the absorption spectrum of the 1.50 mol% Er 2 O 3 : YSZ. The up-conversion spectra produced three prominent peaks at 547(green), 561 (green) and 679 (red) nm. Green and red light maxima were observed with Er 2 O 3 concentrations of 1.5 mol% and 0.5 mol%, respectively. Oscillator strength parameters Ω t (t = 2, 4, 6) were determined using the Judd-Ofelt theory and Ω 2 = 9.90 × 10 −20 cm 2 , Ω 4 = 2.92 × 10 −20 cm 2 , Ω 6 = 3.32 × 10 −20 cm 2 . The Ω 4 /Ω 6 ratio (0.88), which is the key parameter for laser performance of reactive matrix materials , indicates that Er 3+ -doped YSZ has potential laser applications.
研究领域:
材料科学
·
光学
✓ 已验证
DOI
高影响因子
Crystals
·
2022
·Vol. 12
·期 8
·1081
·
IF 2.67
Yazhao Wang,Zhonghua Zhu,Shengdi Ta,Zeyu Cheng,Peng Zhang,Ninghan Zeng,Bernard Albert Goodman,Shoulei Xu,Wen Deng
A series of yttria-stabilized zirconia single-crystals doped with 0.000–0.250 mol% Tb4O7was prepared by the optical floating-zone method. As shown by XRD and Raman spectroscopy, all of the crystals had a cubic-phase structure. These were initially orange–yellow in color, which is indicative of the presence of Tb4+ions, but they then became colorless after being annealed in a H2/Ar atmosphere as a result of the reduction of Tb4+to Tb3+. The absorption spectra of the unannealed samples show both the 4f8→4f75d1transition of Tb3+ions and the Tb4+charge-transfer band. In addition, the transmittance of the crystals was increased by annealing. Under irradiation with 300 nm of light, all of the single-crystal samples showed seven emission peaks in the visible region, corresponding to the decay from the5D3,4excited state of Tb3+to the7FJ(J = 6–0) states. The most intense emission was at 544 nm, which corresponds to the typical strong green emission from the5D4→7F5transition in Tb3+ions.Keywords:yttria-stabilized zirconia;Tb4O7-doped;annealed in H2/Ar atmosphere;optical properties;optical floating-zone method
研究领域:
材料科学
·
光学
✓ 已验证
产品关联
DOI
高影响因子
Crystals
·
2023
·Vol. 13
·期 3
·460
·
IF 2.7
Danni Huang,Tong Xiao,Beibei Fu,Shoulei Xu,Yuyang Huang,Wen Deng,Zhukun Zhou
ZrO2is an attractive host matrix for luminescence material because of its excellent physical properties, such as low phonon energy and wide band gap. In this work, the highly transparent Tm2O3and Yb2O3co-doped yttria stabilized zirconia (YSZ) (abbreviated as Yb/Tm: YSZ) single crystals were grown by the optical floating zone method. The Yb/Tm: YSZ samples were stabilized in the cubic phase at room temperature when Yb3+and Tm3+replaced Y3+. The influence of Yb3+co-doping on the up-conversion luminescence properties of the crystals was systematically studied. A total of 0.5 mol% Tm2O3and 2.0 mol% Yb2O3co-activated YSZ single crystal (abbreviated as 2.0Yb/Tm: YSZ) has the maximum luminous intensity. There were seven absorption peaks located at around 358, 460, 679, 783.3, 850–1000, 1200, and 1721.5 nm that were observed in the absorption spectrum of the 2.0Yb/Tm: YSZ single crystal. There were three up-conversion peaks at around 488, 658 and 800 nm that were observed when the Yb/Tm: YSZ samples were excitated at 980 nm. The fluorescence lifetime of Tm3+for the1G4→3H6transition of the 2.0Yb/Tm: YSZ sample is 7.716 ms as excited with a 980 nm laser. In addition, the oscillator strength parameters Ωλ(λ = 2, 4 and 6) of this sample were derived by the Judd–Ofelt theory to evaluate the laser performance of the host materials. The ratio Ω4/Ω6of this sample is 0.80, implying its excellent laser output. Therefore, the 2.0Yb/Tm: YSZ single crystal is a considerable potential material for laser and luminescence applications.Keywords:YSZ single crystal;Yb3+and Tm3+co-activated;optical floating zone method;up-conversion luminescence;Judd–Ofelt theory
研究领域:
材料科学
·
光学
·
激光物理
✓ 已验证
产品关联
DOI
高影响因子
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