Yb2O3 Phase Research Articles

Nanostructured Yb2SiO5/mullite-SiC/Si environmental barrier coating with long-term stability at 1250 °C

In this work, nanostructured Yb2SiO5/mullite-SiC/Si environmental barrier coatings (EBCs) were prepared to investigate the effect of heat treatment on the microstructure and phase transition of nanostructured Yb2SiO5/mullite-SiC/Si coatings. The Yb2SiO5 content and microstructure evolution in the coatings were thoroughly analyzed before and after heat treatment. The results demonstrate a slight decrease in the porosities of nanostructured Yb2SiO5 and mullite-SiC coatings, accompanied by a gradual growth in grain sizes with increasing heat treatment time, indicating the nanostructured EBCs show good resistance to sintering. Moreover, the thickness of thermal growth oxidation layer is only 200 nm at 1250 °C for 500 h of heat treatment. In particular, the presence of the Yb2O3 phase has been observed to exert a favorable influence on the thermal stability of nanostructured EBCs. This work provides an innovative strategy for designing advanced EBCs with excellent high-temperature thermal stability.

InSb nanoparticles dispersion in Yb-filled Co4Sb12 improves the thermoelectric performance

Out of several methods, one of the most explored strategies to decrease the lattice thermal conductivity of Co4Sb12-based materials are either filling suitable electropositive elements into the voids or the formation of nanocomposites. These two approaches were combined in this work by filling Yb into the void of Co4Sb12 and preparing nanocomposites of Yb0.2Co4Sb12 and InSb according to the formula (InSb)x + Yb0.2Co4Sb12 (where x = 0.1, 0.2, 0.3, 0.4), via ball-milling and spark plasma sintering. Yb2O3 and CoSb2 as impurity phases were found at the grain boundaries. EBSD and TEM micrographs showed nanocrystalline InSb phase (20–200 nm) dispersed in the matrix grains. The charge transfer from Yb filler with an oxidation state of +3 to Co4Sb12 yielded a low electrical resistivity (ρ) of the matrix. An increase in ρ and Seebeck coefficient (S) in the composites with x = 0.1 and 0.3 occurred due to the higher amount of oxide impurities in these two samples and the scattering of charge carriers at the interfaces induced by the secondary phases. The other two composites with x = 0.2 and 0.4 exhibited ρ(T) and S(T) similar to the Yb0.2Co4Sb12 matrix. The dispersion of the InSb and Yb2O3 phases at the grain boundaries combined with the anharmonicity introduced by the fillers (Yb) in the voids enhanced the scattering of phonons within a broad wavelength range and reduced the lattice thermal conductivity significantly. Hence, a highest zT of ~1.2 at 773 K with a thermoelectric efficiency of 8.89% and 8.28% (423–773 K) were obtained for (InSb)0.1 + Yb0.2Co4Sb12 and (InSb)0.2 + Yb0.2Co4Sb12 nanocomposites, respectively.

Properties of Yb-added ZnO (Yb:ZnO) films as an energy-conversion layer on polycrystalline silicon solar cells

Yb-added ZnO (Yb:ZnO) films, as an energy-conversion layer, were formed using a spin-coating technique. As-formed Yb:ZnO films mainly showed the wurtzite structural ZnO phase and a cubic structural Yb2O3 phase appeared at the annealing temperature of 750 °C. The formation route of Yb:ZnO films was proposed as follows: Yb elements did not incorporate into the ZnO host, because of the large difference in ionic radii and the oxidation state of Zn2+ and Yb3+ ions. Thus, diffused Yb elements in the ZnO grains were crystallized independently in the grains during annealing process. The energy-transfer process from the ZnO host to the Yb2O3 nanocomposites occurred efficiently, and the mechanism was followed by a quantum cutting process. The improvement ratio of the power conversion efficiency for the Yb:ZnO-formed glass/pc-Si solar cell (11.7%) compared to that for the bare-glass/pc-Si cell (10.7%) was approximately 9%. Thus, the Yb:ZnO films could be used as an effective energy-conversion layer for Si-solar cells with the benefit of very simple and inexpensive processing.

Water vapor corrosion behaviors of plasma sprayed ytterbium silicate coatings

In this work, the water vapor corrosion behaviors of plasma sprayed ytterbium silicate coatings with different contents of Yb2O3, Yb2SiO5 and Yb2Si2O7 phases were evaluated at 1400oC for 100–300 h and the influence of phase compositions on the corrosion behaviors was analyzed. The results showed that severe corrosion took place in the Yb2Si2O7-rich coating with a porous reacted layer with a thickness about 20 μm after 300 h corrosion. The Yb2O3 phase in the Yb2O3-rich coatings volatilized, lefting a relatively dense reacted layer with a thickness about 5–6 μm after the same corrosion time. A layer composed of Yb2SiO5 was formed on the surface of all the corroded ytterbium silicate coatings. This study may provide theoretical basis for selecting rare-earth silicate environmental barrier coatings (EBCs) with excellent performance.

Interface evolution of Si/Mullite/Yb2SiO5 PS-PVD environmental barrier coatings under high temperature

Plasma spray-physical vapor deposition (PS-PVD) was used to prepare tri-layer environmental barrier coatings (EBCs) Si/mullite/Yb2SiO5 on SiCf/SiC substrate. Isothermal oxidation tests of EBCs were performed at 1300 ℃ for 1000 h. The thermochemical and thermomechanical interface interaction among EBCs were investigated. The results show that more dense EBCs can be obtained through PS-PVD process, which is attributed to the mixed deposition of liquid/gas states. After isothermal oxidation, many pores were observed in the Yb2SiO5 coating near the interface of Yb2SiO5/mullite coating, which results from the diffusion of Yb2O3 phase dissociated from Yb2SiO5 into mullite coating at high temperature. In the mullite coating, the Yb2O3 reacted with Al2O3 generating rod-like Yb3Al5O12 phase. Additionally, due to the thermal expansion mismatch and high temperature oxidation, cracks were formed at the interfaces of mullite/Si coating. Those interface cracks resulted in buckling in the mullite coating.

Formation peculiarities and optical properties of highly-doped (Y0.86La0.09Yb0.05)2O3 transparent ceramics

Abstract Formation peculiarities of highly-doped (Y0.86La0.09Yb0.05)2O3 transparent ceramics have been studied by X-ray diffraction and electron microscopy methods. The phase composition evolution of 1.81Y2O3∙0.18La2O3∙0.01Yb2O3 powder mixtures annealed at the temperatures of 1100, 1200, 1300, and 1400 °C has been studied by XRD. It has been shown that Yb2O3 phase dissolves in Y2O3 matrix in the calcination temperature range of 1300–1400 °C. Complete dissolution of La2O3 in Y2O3 matrix occurs at temperatures above 1400 °C. La3+ ions enter in Y2O3 and Yb2O3 crystal structures simultaneously in the 1200–1300 °C range, which leads to a remarkable increase in the volume of the corresponding crystal lattices. The possible reasons for suppressing the crystalline growth of Y2O3 and Yb2O3 cubic phases have been discussed. Finally, (Y0.86La0.09Yb0.05)2O3 transparent ceramics have been obtained by solid-state vacuum sintering at 1650–1750 °C. Ceramics synthesized at a temperature of 1750 °C have been characterized by an in-line optical transmittance of 60% and a homogeneous distribution of constituent components within the volume and along the grain boundaries.

Microstructure and Thermomechanical Properties of Atmospheric Plasma-Sprayed Yb2O3 Coating

In this study, a Yb2O3 coating was fabricated by the atmospheric plasma spray technique. The phase composition, microstructure, and thermal stability of the coating were examined. The thermal conductivity and thermal expansion behavior were also investigated. Some of the mechanical properties (elastic modulus, hardness, fracture toughness, and flexural strength) were characterized. The results reveal that the Yb2O3 coating is predominantly composed of the cubic Yb2O3 phase, and it has a dense lamellar microstructure containing defects. No mass change and exothermic phenomena are observed in the thermogravimetry and differential thermal analysis curves. The high-temperature x-ray diffraction results indicate that no phase transformation occurs from room temperature to 1500 °C, revealing the good phase stability of the Yb2O3 coating. The coefficient of thermal expansion of the Yb2O3 coating is (7.50-8.67) × 10−6 K−1 in the range of 200-1400 °C. The thermal conductivity is about 1.5 W m−1 K−1 at 1200 °C. The Yb2O3 coating has excellent mechanical properties and good damage tolerant. The unique combination of these properties implies that the Yb2O3 coating might be a promising candidate for T/EBCs applications.

Yb2O3 nanowires, nanorods and nano-square plates

Developing a new morphology and revealing new physicochemical properties are very important steps in industrial applications. In this study, ytterbium oxide (Yb2O3) nanowires, nanorods and nano-square plates were first synthesized by a facial hydrothermal method and a post-thermal treatment, and characterized by X-ray diffraction crystallography, Fourier transform-infrared, UV–visible-NIR absorption, photoluminescence, and X-ray photoelectron spectroscopy. The morphology and the microstructures were examined by scanning electron microscopy and high resolution transmission electron microscopy. As-prepared samples with different morphologies showed different crystal phases but changed to the same cubic Yb2O3 phase upon thermal treatment. Eu(III) and Tb(III) activator ions were also doped into Yb2O3 host materials and discussed.

Structure and thermal expansion of Lu2O3 and Yb2O3 up to the melting points

Knowledge of thermal expansion and high temperature phase transformations is essential for prediction and interpretation of materials behavior under the extreme conditions of high temperature and intense radiation encountered in nuclear reactors. Structure and thermal expansion of Lu2O3 and Yb2O3 were studied in oxygen and argon atmospheres up to their melting temperatures using synchrotron X-ray diffraction on laser heated levitated samples. Both oxides retained the cubic bixbyite C-type structure in oxygen and argon to melting. In contrast to fluorite-type structures, the increase in the unit cell parameter of Yb2O3 and Lu2O3 with temperature is linear within experimental error from room temperature to the melting point, with mean thermal expansion coefficients (8.5 ± 0.6) · 10−6 K−1 and (7.7 ± 0.6) · 10−6 K−1, respectively. There is no indication of a superionic (Bredig) transition in the C-type structure or of a previously suggested Yb2O3 phase transformation to hexagonal phase prior to melting.

Study on the structure and properties of (1-x) BiYbO3-xBaTiO3 ceramics synthesized by sol–gel method

ABSTRACT(1-x) BiYbO3-xBaTiO3 (short for BY-BT) lead-free ferroelectric ceramics were synthesized by solid state reaction method. The microstructure, dielectric and ferroelectric properties were studied as a function of the relative ratio between the two ceramics. It is found that all samples calcined at 800°C and sintered at 1050°C consist of Bi1.3Yb0.7O3 and Yb2O3 phases, which shows relatively high density. The highest relative density (ρ = 99.8%) and shrinkage (α = 13%) of BY-BT ceramics is obtained at x = 0.05. The maximum value of the remanent polarization (Pr) (Prmax = 0.1286 μC/cm2) can be obtained when x = 0.1. These results indicate a possible treat method to optimize the properties of two solid solutions.

Facile Fabrication and Characterization of Ytterbium Oxide Hollow Spheres using Carbon Spheres as Template

Uniform rare-earth ytterbium oxide (Yb2O3) hollow microspheres have been successfully prepared via a urea-based homogenous precipitation method using carbon spheres as template, followed by a heat treatment. The main synthesis process was carried out in aqueous conditions without any organic solvents, surfactants or etching agents. X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetry, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, Brunauer–Emmett–Teller surface area measurement were employed to characterize the samples. The results show that the final products can be indexed to cubic Yb2O3 phase with high purity. The as-obtained Yb2O3 microspheres with spherical shape and hollow structure are uniform in size and distribution of about 450[Formula: see text]nm and wall thickness of approximately 15[Formula: see text]nm.

Optical properties of Yb-doped ZnO/MgO nanocomposites

Yb3+ doped ZnO/MgO nanocomposite were prepared by combustion synthesis method. The samples were further heated to 1000°C to improve their crystallinity and photoluminescent efficiency. The concentrations of Yb3+ and Mg2+ were varied between 1–2% and 5–70% respectively in prepared samples. The nano-powders were characterized by Scanning Electron Microscopy and X-ray Diffraction for morphology and structural determination. XRD studies have revealed the wurtzite structure for MgxZn1−xO for Mg concentrations below 30%. Higher concentrations of Mg results in Yb3+ doped ZnO/MgO nanocomposite containing three phases; the wurzite hexagonal phase typical of ZnO, the cubic phase of MgO and a small amount of cubic Yb2O3 phase. As expected, the amount of cubic phase in nano-powders increased with the increase of Mg concentration in ZnO. The crystallite size of ZnO/MgO composites decreased from 55nm to 30nm with increase of Mg content. SEM images of Yb3+ doped ZnO/MgO nanocomposite with higher Mg content (>50%) showed clearly distinct hexagonal and cubical shaped nano-particles. Photoluminescent emission showed a broad band in the range (435nm to 700nm). Pure ZnO nano-phosphor showed an emission peak around 545nm, which is blue shifted with Mg content. The photoluminescence intensity increased with increase of Mg content in ZnO and it became maximum with 30% Mg concentration. Time resolved decay curves of photoluminescence indicated decay time in microsecond time scale.

Influence of Yb2O3 doping on microstructural and electrical properties of ZnO-Bi2O3-based varistor ceramics

ZnO-Bi2O3-based varistor ceramics doped with Yb2O3 in the range from 0 to 0.4% (molar fraction) were obtained by a solid reaction route. The X-ray diffractometry (XRD) and scanning electron microscopy (SEM) were applied to characterize the phases and microstructure of the varistor ceramics, and a DC parameter instrument for varistor ceramics was applied to investigate their electrical properties and V–I characteristics. The XRD analysis of the samples shows that the ZnO phase, Bi2O3 phase, Zn7Sb2O12-type spinel phase and Zn2Bi3Sb3O14-type pyrochlore are present, and the Yb2O3 phases and Sb2O4 phases are found in varistor ceramics with increasing amounts of Yb2O3. The average size of ZnO grain firstly increases and then decreases with the increase of Yb2O3 content. The result also shows that the threshold voltage is between 656 V/mm and 1 232 V/mm, the nonlinear coefficient is in the range of 14.1–22.3, and the leakage current is between 0.60 μA and 19.6 μA. The 0.20% Yb2O3-added ZnO-Bi2O3-based varistor ceramics sintered at 900 °C have the best electrical characteristics.

Structural and Chemical Characterization of Yb2O3-ZrO2 System by HAADF-STEM and HRTEM

ZrO2:Yb3+ nanocrystalline phosphors with high concentrations of ytterbium ions were prepared using the sol-gel method. X-ray diffraction, high-angle annular-dark-field scanning transmission electron microscopy (HAADF-STEM), energy dispersive X-ray spectroscopy, and high-resolution transmission electron microscopy (HRTEM) were used to characterize the nanocrystalline phosphors annealed at 1000 degrees C. Unit-cell distortion and changes in the crystalline structure of the monoclinic zirconia to tetragonal zirconia, and subsequently cubic zirconia, were observed with increased Yb concentration. Yb ions were randomly distributed into the lattice of the crystalline structure. No segregation of Yb2O3 phase was observed. The substitution of Zr atoms by Yb atoms on different crystalline phases was confirmed by the experimental results and theoretical simulations of HRTEM and HAADF-STEM.

Al2O3-ZrO2-Yb2O3 phase diagram. IV. Vertical sections

For more complete presentation of the Al2O3-ZrO2-Yb2O3 phase diagram, three vertical sections are constructed over a wide temperature and composition range. The bisector Al2O3/ZrO2 = 1 discovers the Yb2O3-rich corner of the ternary phase diagram and explains the mechanism of Yb2O3 phase transformation H ⇄ C. The isopleth 15 mole% ZrO2 (15Z) shows the Al2O3-ZrO2-Yb2O3 structure near the Al2O3-Yb2O3 bounding binary system. The bisector Al2O3/Yb2O3 = 1 depicts the ternary system in the ZrO2-rich region. The vertical sections intersect each of the three triangulating sections of the Al2O3-ZrO2-Yb2O3 system and demonstrate the width variation of its two-phase regions.

Influence of annealing temperature on the luminescence of Er/Yb co-doped Al2O3 films

The influence of annealing temperature on the photo-luminescence (PL) of high co ncentration Er/Yb co-doped Al２O３ films was studied. The relationship betwe en PL spectra and microstructure of the films at various annealing temperatures was revealed by analyzing the dependence of the intensity and the full width at half-maximum of the PL spectra on the annealing temperature. The PL measurement shows that the annealing behavior may be split into three different regimes. Bel ow 750℃, the intensity increases with the increase of annealing temperature wit h a small slope, which corresponds to the amorphous Al２O３ films. Between 800℃ and 900℃, the PL intensity increases considerably, where the microstructure of the films was identified to be composed of γ-Al２O３ grains in nano-meter scale; At the temperature of 1000℃, the intensity of PL spectrum decre ases to a very low level, γ-Al２O３ grains and the segreg ation of Er2O ３ and Yb2O３ phases were observed by using transmis sion electron microscopy . Furthermore, the dependence of PL spectrum shape on the PL intensity of sub-le vel transition was analyzed and discussed by fitting the PL spectra at various t emperatures．