Y2O3 Stabilizer Research Articles

Influence of Y2O3 doping on the aging behavior and mechanical properties of ATZ ceramics

The aim of this study was to investigate the influence of the Y2O3 content on the mechanical properties and aging behavior of ATZ ceramic. For this purpose, an ATZ ceramic consisting of 80 wt% stabilized ZrO2 and 20 wt% Al2O3 with varying Y2O3 stabilizer content between 2 and 3 mol% was prepared. The samples were analyzed regarding their sintered density, grain size, hardness and fracture toughness. The results show an increase in fracture toughness and a decrease in hardness with decreasing Y2O3 content. In addition, the aging stability was assessed by analyzing the phase composition determined by X-ray diffraction after aging the samples for up to 150 hours in steam atmosphere at 134 °C and 2 bar. The aging stability decreases with decreasing stabilizer content. Nevertheless, by producing a very fine-grained material, high aging stability can be achieved despite reduced Y2O3 content.

Fabrication of Y2O3–CaO composite ceramics with controllable hydration resistance by a novel gel casting method

Y2O3 and CaO are ideal ceramic materials for precision casting of TiAl alloy, overcoming challenges associated with intricate component removal, such as turbine blades, leveraging the stability of Y2O3 and the water solubility of CaO. To address these challenges, we employed Isobam104 in a novel gel casting method, serving as both a dispersant and a gelling agent. This method enabled us to create a stable Y2O3–CaCO3 slurry with high solid content (up to 55 vol%) and low viscosity (101.51 mPa·s at a shear rate of 10 s−1). Following sintering at 1500 °C for 2 h, Y2O3–CaO composite ceramics were produced. Surprisingly, two distinct characteristics of CaO were noted. One showed a rod-shaped morphology with high chemical reactivity crucial for water solubility, while the other displayed a flat-like feature, forming a well-maintained interface due to its coherent or semi-coherent matching relationship with Y2O3, thereby providing excellent hydration resistance. Ultimately, we acquired composite ceramics showcasing a 30-day “shelf life" alongside exceptional water solubility. This establishes the theoretical groundwork for storing and employing soluble ceramic cores in the precision casting of TiAl alloy.

High-temperature phase stability of Y2O3 and SiO2 co-doped ZrO2 powder

High-temperature phase stability of Y2O3 and SiO2 co-doped ZrO2 powder

Stability of Y2O3:Tm,Yb phosphor thin films during cathodoluminescence and upconversion

An Y2O3:Tm,Yb thin film was synthesized by the sol-gel method using spin coating. X-ray powder diffraction revealed the formation of a Y2O3 cubic phase. The cathodoluminescence and upconversion photoluminescence of the film were investigated, including assessment of emission stability. Auger electron spectroscopy was used to monitor its chemical state concurrently with the cathodoluminescence intensity using the same electron beam. Auger peaks associated with carbon, yttrium and oxygen were detected and their Auger peak-to-peak heights indicated that carbon was removed from the surface during the initial stage of degradation, whereas yttrium and oxygen remained almost unchanged. The cathodoluminescence degradation of the Tm emissions at 457 nm and 975 nm exhibited a continuous decline until the electron dose was about 100 C/cm2 and then stabilized. The upconversion photoluminescence intensity of the Tm emission at 488 nm remained stable for a period of 28 h and did not exhibit degradation.

Stability and plasma etching behavior of yttrium-based coatings by air plasma spray process

In recent days, many studies have focused on fluorine-saturated yttrium-based coatings for better material performance in semiconductor processing chambers. In this investigation, yttrium oxide (Y2O3) and yttrium oxyfluoride (YOF) powders were synthesized using a simple solid-state wet chemical process. Then, the Y2O3 and YOF powder feedstocks were coated on an aluminum (Al) substrate using the atmospheric plasma spraying (APS) technique at different plasma powers of 25.6, and 25.2, 33.2 kW, respectively. Microstructure, macroscopic property, and chemical stability of dense Y2O3 and YOF-coated samples were analyzed. The Vickers hardness values of Y2O3 and YOF coated samples were 369.2 ± 32, and 267.1 ± 25, 241.9 ± 31 at plasma powers of 25.6, and 25.2, 33.2 kW, respectively. Y2O3 sample was showed higher hardness value due to less porosity. The etching behavior of the Y2O3 and YOF coatings was analyzed using PECVD- NF3 plasma. X-ray photoelectron spectrum analysis (XPS) has confirmed the fluorination on the etched surfaces. The relative intensity ratios of the YF to YO peaks on the Y2O3 and YOF coatings after exposure to NF3 plasma were 1.30 and 1.48, respectively. This indicated that the YOF coating showed a strong fluorination layer and superior resistance for fluorine-plasma exposure compared to Y2O3, which is more appropriate for use as a protective material for the inner wall reactors. Therefore, YOF coated samples have good stability with high erosion resistance, which is highly suggested for applications in the semiconductor industry.

Effect of thermal treatment at high temperature on phase stability and transformation of Yb2O3 and Y2O3 co-doped ZrO2 ceramics

Y2O3 doped ZrO2 (YSZ) ceramic material is used to protect alloy components worked in high-temperature. But its phase transformation between tetragonal phase and monoclinic phase occurred at 1150 °C leads to YSZ invalid. Therefore, enhancing the phase stability of YSZ is necessary for meeting the demands of the development of thermal barrier coatings (TBC). In this study, X-ray diffraction and Raman spectra were used to explore the phase stability and phase transformation of Yb2O3 and Y2O3 co-doped ZrO2 (YbYSZ) ceramics after heat treatment at 1300 °C with different times. The stability of tetragonal phase is improved by tetragonality decreasing with Yb3+ doped. Simultaneously, the incorporation of Yb3+ leads to O–O coupling, which is beneficial for increasing the concentration of oxygen vacancies near the substituted ions, thereby improving the stability of the crystal. The 6.5YbYSZ ceramic has the best stability after heat treatment at 1300 °C for different times.

Improving Electrochemical Cycling Stability of Ni‐rich LiNi0.91Co0.06Al0.03O2 Cathode Materials through H3BO3 and Y2O3 Composite Coating

AbstractThe nickel‐rich LiNi0.91Co0.06Al0.03O2 cathode material has attracted wide attention due to its high energy density and appropriate thermal stability; however, its practical application has been greatly restricted by exorbitant residual LiOH/Li2CO3 and poor cycling performance. In this work, we have reduced the residual LiOH/Li2CO3 by washing the LiNi0.91Co0.06Al0.03O2 fabricated through a high‐temperature solid‐state method and improved the cycling performance with a composite coating process. The results show that the amount of residual LiOH/Li2CO3 in the washed materials is significantly decreased, which is very favorable for the processability of materials. LiNi0.91Co0.06Al0.03O2 with 0.1 wt% composite coating exhibits optimum properties: the discharge capacity reaches 217.4 mAh/g at 0.1 C, the cycling retention still remains at 93.7 % after 100 cycles at 1 C, and the cycling retention of the soft‐packing battery remains as high as 81.7 % after 800 cycles at 1 C. The excellent electrochemical performances are attributed to the synergistic effect of excellent fluidity of H3BO3 and outstanding stability of Y2O3, mitigating the interface reaction between electrolyte and cathode material.

Sintering and hot corrosion of yttria silicate tablets in molten salts prepared by spark plasma sintering

Purpose This paper aims to study the microstructural hot corrosion behaviour of the sintered Y2SiO5 ceramic silicate under a Na2SO4 + V2O5 mixture at an engine representative temperature of 1150°C. Y2SiO5 is a promising candidate for thermal barrier coatings (TBC) due to its excellent chemical stability at high temperatures. As a continuous source of Y3+, it is expected that Y2SiO5 environmental barrier coating may prolong the lifetime of TBC systems by stopping the degradation caused by the loss of the Y2O3 stabilizer. Design/methodology/approach Two routes were chosen for the yttria silicate powder synthesis by sol-gel from TEOS and APTES precursors as the difference in Si source changed the ratio of Y2SiO5/Y2Si2O7 phases. Hot corrosion studies using Na2SO4 and V2O5 mixtures were conducted on both surfaces of APTES and TEOS tablets at 1150°C for 8 h in atmospheric air. The morphology and microstructure analyses of the silicate samples after hot corrosion tests were carried out using a SEM and X-ray diffraction analyse techniques. Findings Based on the degradation, the general status of the APTES tablet after hot corrosion presents a better hot corrosion resistance at a temperature of 1150°C than does that of the TEOS tablet. In the TEOS tablet, the crystal morphology of NaY9Si60O26 woodchip shapes with a size of 60 µm is developed on the surface for finally initiating some cracks. In the APTES case, the crystal morphology of rod-like shapes with a size of 100 µm is developed; hence, a dense thick layer predominately postpones the reaction of V2O5 and Na2SO4 with yttria silicate, and consequently, less damage is observed. Originality/value Coating yttria silicate preparation is very complicated; the problems of a high synthesis temperature, long production period and low yield still need to be solved. Under these perspectives, ceramics prepared via spark plasma sintering (SPS) can reach theoretical high densities and a fine grain size can be retained after the SPS process; hence, well resistance to the corrosion in molten salts is expected to obtain for the sintered yttria silicate tablets.

Insight into the pressure effect on the structural stability and physical properties of cubic sesquioxides X2O3 (X= Sc, Y and In)

The structural stability, elastic properties and elastic anisotropy of cubic sesquioxides Sc2O3, Y2O3 and In2O3 under pressure are systematically investigated using the first-principles calculations. For three materials, the pressure dependent behaviors of the structural stability and mechanical properties are investigated from 0 to 15 GPa. The formation enthalpy, volume change, phonon frequencies and mechanical stability confirm that cubic Sc2O3, Y2O3 and In2O3 exhibit the structural stability at ground state and high pressure. The elastic constants, elastic moduli and anisotropy increase with the increasing pressure. The pressure promotes that the ductile ability and the anisotropic degree increase with the increasing pressure.

Chemically and thermally stable lanthanide-doped Y2O3 nanoparticles for remote temperature sensing in catalytic environments

Luminescent nanoparticles have great potential for remote temperature sensing. Mapping of high temperature profiles under harsh conditions that are common in chemical reactors requires new thermally and chemically stable (nano)probes. Here, we report temperature dependent luminescence of Yb3+/Er3+-, Dy3+- and Eu3+-doped Y2O3 nanoparticles (NPs). We have deposited these lanthanide-doped Y2O3 NPs on α-Al2O3, a non-porous catalyst support material. The NPs are strongly adsorbed on the surface and no sintering was observed upon heating to 900 K for 12 h. The high chemical and thermal stability of Y2O3 makes these nanoprobes ideal for sensing in catalytic environments. A systematic study of the three types of luminescent NPs reveals that the temperature dependent luminescence of Yb3+/Er3+, Dy3+ and Eu3+ serves different temperature ranges: lower T regime (300–800 K, accuracy < 5 K) for Yb3+/Er3+, intermediate T for Dy3+ (400–900 + K, accuracy < 15 K) and high T for Eu3+ (550–900 + K, accuracy < 12 K). The superior thermal and chemical stability of the Y2O3/α-Al2O3 host in combination with different luminescent lanthanide dopants results in a robust system that can be tailored to monitor temperatures in different regimes with the highest possible sensitivity.

Improved stability of Y2O3 supported Ni catalysts for CO2 methanation by precursor-determined metal-support interaction

Y2O3 supported Ni catalysts were prepared from different Y precursors. The catalysts synthesized via Y4O(OH)9(NO3) and YO(NO3) as precursors exhibit superior activity in CO2 methanation reaction compared to the catalysts prepared by direct impregnation of Y2O3. YO(NO3) acts as a unique matrix to afford anchoring sites to interact with Ni2+ ions, leading to a moderate interaction between Ni metal and Y2O3 support, which translates into excellent catalytic activity and stability towards CO poisoning. In situ DRIFTS spectra confirm the reaction mechanism of Ni/Y2O3 catalyzed CO2 methanation with carbonates and formates as the key intermediates. The apparent difference in the rate of transformation of formates into methane determines catalytic activity of these Ni/Y2O3 catalysts. This work provides an effective strategy to achieve CO2 activation and resistance to CO poisoning through careful selection of precursor for the support, which allows to control the strength of metal-support interaction.

Effect of HfN, HfC and HfB2 additives on phase transformation, microstructure and mechanical properties of ZrO2-based ceramics

ZrO2-based ceramics were fabricated by the hot pressing sintering technology at 1550℃. Effect of HfN, HfC and HfB2 additives on their phase transformation, microstructure and mechanical properties were investigated. The m-ZrO2 was not discovered in ZrO2-HfC ceramics but discovered in ZrO2-HfN and ZrO2-HfB2 ceramics, which indicated that HfC potentiated the effect of Y2O3 stabilizer on inhibiting phase transformation and that to some extend HfN and HfB2 undermined this effect. Meanwhile, HfC can inhibit the ZrO2 grain growth or amalgamation to form fine ZrO2 grains in ZrO2-HfC ceramics, whereas HfN and HfB2 probably induced the ZrO2 grain growth or amalgamation to form big ZrO2 grains in their ceramics. And the bonding strength between HfB2 and ZrO2 higher than the other two was approximately inferred from the observed grain boundary-interface dihedral angles between the ZrO2 grain and these particles (HfC, HfN and HfB2). Fracture model of these ceramics was the mixed inter/transgranular fracture model. When the additive content – HfN, HfC and HfB2 content - increased from 5wt% to 15wt%, the pinning effect of HfN particle in ZrO2-HfN ceramics as well as fine ZrO2 grains in ZrO2-HfC ceramics and the high bonding strength between the ZrO2 grain and HfB2 particle in ZrO2-HfB2 ceramics played a dominant role in improving the flexural strength and fracture toughness; meanwhile, the improved Vickers hardness of these ceramics was mainly attributed to the increase of hard additive content. However, when these additives content increased to 20wt%, many big micro-voids in ZrO2-HfN and ZrO2-HfC ceramics and big ZrO2 grains in ZrO2-HfB2 ceramic produced negative effect on mechanical properties. In these ceramics, ZrO2-15wt%HfB2 ceramic showed the optimum mechanical properties: flexural strength of 1093.06 ± 24MPa, fracture toughness of 8.17 ± 0.18MPam1/2 and Vickers hardness of 14.37 ± 0.21GPa.

Application of high-temperature ceramic plasma-spray coatings for a reusable melting crucible

Metallic fuels, such as the U-Zr alloy system for sodium-cooled fast reactor (SFR), are melted in a Y2O3 slurry-spray-coated graphite crucible in order to prevent melt/material interactions. Reactive and porous coatings such as the Y2O3 slurry-spray-coating are a source of melt contamination and fuel loss, respectively. Therefore, a dense plasma-spray coating of non-reactive materials is desirable for a reusable melting crucible. In this study, ceramic materials such as Y2O3 and 8mol% Y2O3-st. ZrO2, are selected as candidate protective coating materials for reusable crucibles for melting metallic fuel slugs. Studies are conducted to characterize the thermal cycling performance of the coatings, and the interactions between the U-10wt% Zr fuel and the coating layer on the substrates. The thermal cycling tests of the ceramic plasma-spray coatings exhibit good thermal cycling characteristics with few interconnected cracks. The Y2O3 plasma-spray coating does not form a significant reaction layer between the melt and the coating layer due to the thermodynamic stability of Y2O3. Hence, the Y2O3 plasma-spray coating exhibits the most promising performance among the ceramic coatings investigated, for use in reusable melting crucibles.

The photoluminescent properties of Y2O3:Bi3+, Eu3+, Dy3+ phosphors for white-light-emitting diodes.

Bi3+, Eu3+, Dy3+ activated Y2O3 phosphors were prepared through the sol-gel process. X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectra, and photoluminescence (PL) spectra were used to characterize the resulting phosphors. The XRD patterns show the refined crystal structure of Y2O3. The energy transfer processes of Bi(3+)-Eu3+ occurred in the host lattices. The thermal stability of Y2O3:Bi3+, Eu3+, Dy3+ phosphors was studied. Under short wavelength UV excitation, the phosphors show excellent characteristic red, blue, and yellow emission with medium intensity.

Luminescence properties of Y2O3:Eu3+ nanocrystals prepared by the ultrasonic chemistry method.

Y2O3:Eu3+ nanocrystals were prepared by ultrasonic chemistry and characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The resulting nanocrystals were found to be nanoparticles with size distribution in the range of 50-80 nm. The phase of all the samples was cubic. The luminescence properties of the samples were systematically studied and show significant change with concentration of surfactant and annealing temperature. The results show that the intensity of the excitation and emission spectra of Y2O3:Eu3+ nanocrytals increases gradually with increasing P123 concentration and annealing temperature. The fluorescence lifetime of 5D0 level Eu3+ decreases with increasing P123 concentration and increases with annealing temperature. The photoluminescence stability of Y2O3:Eu3+ nanocrytals becomes worse with increasing P123 concentration and annealing temperature.

3Y-TZP ceramics with improved hydrothermal degradation resistance and fracture toughness

Different factors such as the way of incorporating the Y2O3 stabilizer, alumina addition and sintering temperature were assessed with the goal to improve the low temperature degradation (LTD) resistance of 3Y-TZP without compromising on the mechanical properties. The degradation of hydrothermally treated specimens was studied by X-ray diffraction, micro-Raman spectroscopy and scanning electron microscopy. Decreasing the sintering temperature decreased the LTD susceptibility of 3Y-TZPs but did not allow to obtain a LTD resistant 3Y-TZP with optimized mechanical properties. Alumina addition along with the use of Y2O3 stabilizer coated starting powder allowed to combine both an excellent toughness and LTD resistance, as compared to alumina-free and stabilizer co-precipitated powder based equivalents. Transmission electron microscopy revealed that the improved LTD resistance could be attributed to the segregation of Al 3+ at the grain boundary and the heterogeneously distributed Y 3+ stabilizer. © 2014 Elsevier Ltd. All rights reserved.

Enhanced stability of hafnia based coatings in a hot gas environment

Yttria stabilized hafnia (YSH) coatings have been fabricated by magnetron sputtering, a physical vapor deposition (PVD) method. Coatings of a mixed composition of hafnia (HfO2) and zirconia (ZrO2) (YSHZ) stabilized by yttria (Y2O3) were also fabricated in order to compare and contrast the resulting properties. The composition of the material was varied by varying the ratio of HfO2 and ZrO2 (4:1, 2:1, 1:1, 1:2 and 1:4) while keeping the Y2O3 stabilizer content constant at 7.5 mol%. Thermal and chemical stability along with the durability of the YSH and YSHZ coatings were evaluated by exposing the coatings to hot gases in a combustor rig. A nanoindentation technique was used to evaluate the mechanical properties. A diamond tipped, sharp nanoindenter with known geometry and mechanical properties was forced into the sample while both the force and indentation depth were recorded. Hardness (H) and Young's modulus were estimated for the YSH and YSHZ coatings. Atomic force microscopy was utilized to provide imagery of the indentation area on the sample surface. Residual stress analysis was performed using X-ray diffraction (XRD). The results from nano-indentation indicate that the YSH sample possesses values of hardness and Young's modulus as high as 18 GPa and 220 GPa, respectively. The residual stress estimated using XRD indicates very high compressive stress within the coatings. The stability and durability tests demonstrate the enhanced stability of YSH coatings in a hot gas environment created by burning natural gas with oxygen.

Effect of composition on the growth and microstructure of hafnia–zirconia based coatings

Yttria (Y2O3)–stabilized hafnia (HfO2)–zirconia (ZrO2)-based coatings were grown and studied for their growth and microstructure. Composition of the coatings was varied by varying the ratio of HfO2 and ZrO2, from 1:4 to 4:1, while maintaining the Y2O3 stabilizer content fixed at 7.5mol%. The crystal structure, surface morphology and thermal stability of the grown coatings were evaluated as a function of the coatings' composition. The crystal structure analysis performed by X-ray diffraction (XRD) indicates the hafnia-cubic-phase stabilization in all the coatings. The morphology of the coatings is characterized by the columnar growth coupled with a dense structure as revealed by the scanning electron microscopy (SEM). Thermal stability evaluation performed using high temperature XRD coupled with SEM indicates the enhanced stability of these coatings to 1300°C. No significant changes were found in the crystal structure and morphology of the coatings.

Hydrothermal Synthesis and Mechanical Characterization of ZrO2 by Y2O3 Stabilizer Contents

In this study, partially stabilized zirconia was synthesized using a chemical <TEX>$Y_2O_3$</TEX> stabilizer and hydrothermal method. First, <TEX>$YCl_3-6H_2O$</TEX> and <TEX>$ZrCl_2O-8H_2O$</TEX> was dissolved in distilled water. Y-TZP (a <TEX>$Y_2O_3$</TEX>-doped toughened zirconia polycrystalline precursor) was also prepared by conventional co-precipitates in the presence of an excess amount of <TEX>$NH_4OH$</TEX> solution under a fixed pH of 12. The Y-TZP precursors were filtered and repeatedly washed with distilled water to remove <TEX>$Cl^-$</TEX> ions. <TEX>$ZrO_2$</TEX>-Xmol%<TEX>$Y_2O_3$</TEX> powder was synthesized by a hydrothermal method using Teflon Vessels at <TEX>$180^{\circ}C$</TEX> for 6 h of optimized condition. The powder added with the Xmol%- <TEX>$Y_2O_3$</TEX> (X = 0,1,3,5 mol%) stabilizer of the <TEX>$ZrO_2$</TEX> was synthesized. The crystal phase, particle size, and morphologies were analyzed. Rectangular specimens of <TEX>$33mm{\times}8mm{\times}3$</TEX> mm for three-point bend tests were used in the mechanical properties evaluation. A teragonal phase was observed in the samples, which contains more than 3 mol% <TEX>$Y_2O_3$</TEX>. The <TEX>$3Y-ZrO_2$</TEX> agglomerated particle size was measured at <TEX>$7.01{\mu}m$</TEX>. The agglomerated particle was clearly observed in the sample of 5 mol % <TEX>$Y_2O_3-ZrO_2$</TEX>, and and the agglomerated particle size was measured at 16.4 um. However, a 20 nm particle was specifically observed by FE-SEM in the sample of 3 mol% <TEX>$Y_2O_3-ZrO_2$</TEX>. The highest bending fracture strength was measured as 321.3 MPa in sample of 3 mol% <TEX>$Y_2O_3-ZrO_2$</TEX>.

Effects of Al doping and annealing on chemical states and band diagram of Y2O3∕Si gate stacks studied by photoemission and x-ray absorption spectroscopy

The authors have investigated the effects of Al doping and annealing on the photoemission spectra and thermal stability of Y2O3∕Si gate stacks by photoemission spectroscopy and x-ray absorption spectroscopy. They have found that the SiO2 components diffuse into the Y2O3 layer by annealing, resulting in the formation of Y silicate; however, the formation of metallic Y silicide is not observed. The changes in valence- and conduction-band offsets by doping Y2O3 with Al with respect to both Al concentration and annealing temperature have been systematically investigated. With an increase in the Al concentration, the band offsets and band gaps increase and the conduction-band edges change nonlinearly.