Influence of multi-step annealing on nanostructure and surface morphology of Y2O3:SiO2 powder

Y₂O₃:SiO₂ powder was synthesized by a sol–gel method, using hydrous yttrium nitrate and hydrous silicon oxide as precursors and HCl as a catalyst. The dried samples were submitted to multi-step annealing schedule in air without applying pressure. A simple four-step annealing schedule with a final stage of about 900 °C for 6.0 h was followed. The samples of Y₂O₃:SiO₂ nanocomposites were obtained with well defined size and shape. Structural changes of the nanocomposites were investigated by XRD, FTIR and TEM. Multi-step annealing scheme with different ramp rates and incubation times allows recovery-relaxation processes within the boundaries and leading to a concomitant linear increase of crystallite size and densification. Almost fully dense quasi-spherical cubic-yttria nanopowder has been demonstrated with an average grain size distribution of 10–40 nm; can be uniformly dispersed in silica matrix.     

Hot Pressing of Infrared‐Transparent Y2O3–MgO Nanocomposites Using Sol–Gel Combustion Synthesized Powders

A sol–gel combustion method has been used to synthesize Y₂O₃–50 vol%MgO composite nanopowders. Solutions of the precursor nitrates were mixed with citric acid and ethylene glycol, heated from 200°C to a predetermined temperature gradually, giving nanocrystalline ceramic powders. The influence of the ratio of yttrium nitrate to the whole precursor mixture and the holding temperature on the properties of the composite nanopowder was investigated using a combination of thermal analysis, X‐ray diffraction, specific surface area analysis, and scanning electron microscopy techniques. When the ratio of yttrium nitrate to the whole precursor mixture reaches 22.5 mol%, the average particle size of synthesized composite nanopowder is 13 nm and the specific surface area is 45.9 m²/g. Then the synthesized Y₂O₃–MgO composite nanopowder was consolidated by the hot‐pressing technique at 1200°C with different dwell time. As a result, the nanocomposite ceramic prepared with a dwell time of 60 min got the highest transmittance of 75% at 5 μm wavelength. The cut‐off wavelength of Y₂O₃–MgO nanocomposite ceramic reaches 9.8 μm, which is superior to other mid‐IR transparent materials. In addition, the fabricated sample is more or less transparent in visible wavelengths and the transmittance at 0.8 μm is as high as 14.5%.     

Preparation of uniformly dispersed YAG ultrafine powders by co-precipitation method with SDS treatment

Uniformly dispersed yttrium aluminum garnet (Y₃Al₅O₁₂, YAG) ultrafine powders were synthesized by co-precipitating a mixed solution of aluminum and yttrium nitrates with ammonium hydrogen carbonate in the presence of sodium dodecyl sulfate (SDS) as dispersing agent. The primary purpose of introducing SDS was to protect YAG particles from agglomeration. The evolution of phase composition and micro-structure of the as-synthesized YAG powders were characterized by thermogravimetry/differential scanning calorimetry, X-ray diffraction, infrared spectra and scanning electron microscopy. The results showed that phase-pure YAG powders could be achieved by calcination of the precursor at 900 °C for 2 h. Uniformly dispersed YAG powders with a particle size of approximately 90-100 nm were obtained with optimum molar ratio of Al³⁺ to SDS at 2. And excessive SDS restrained good dispersion of the YAG powders. The dispersion mechanism of SDS in the preparation process was discussed.     

Synthesis and reaction sintering of YB4 ceramics

Within this work, the preparation of yttrium tetraboride (YB₄) in the form of powder as well as bulk material was investigated.Powders were synthesized via four different reaction methods, including direct synthesis from elemental powders, reduction of yttrium oxide with boron, boron carbide reduction, and combined boron carbide/carbothermal reduction at 1500 °C, 1700 °C and 1900 °C. Pure YB₄ powder was successfully synthesized using the combined boron carbide/carbothermal reduction method. Secondary phases, especially Y₂O₃, YB₂ or YBO₃, were found in powders prepared using the other three methods.Bulk material was prepared using direct synthesis from elements by reactive hot-pressing. Influence of temperature and boron content on densification and phase evolution of samples was studied. In situ reaction sintering was performed using conventional hot-pressing at temperatures from 1100 °C to 1800 °C in vacuum. The amount of boron varied from the stoichiometric content to 5 and 10 wt% excess (with respect to the reaction from elemental powders). Stoichiometric reactions led primarily to the formation of YB₂ and YB₄ and several secondary phases such as Y₂O₃, YBO₃ and Y_16.86B₈O₃₈. YB₄ as a main phase was formed only at elevated temperatures (1700 °C and 1800 °C) but certain content of impurities was still present. Excess of B resulted in the formation of YB₄ as a primary phase in all prepared samples with a small content of YBO₃ and/or Y_16.86B₈O₃₈. Moreover, SEM analysis revealed the presence of unreacted boron.     

Nonisothermal crystallization behaviors and conductive properties of PEO‐based solid polymer electrolytes containing yttrium oxide nanoparticles

Lithium solid polymer electrolytes (SPE) composed of polyethylene oxide (PEO) and yttrium oxide (Y₂O₃) nanoparticles were prepared. The influence of the Y₂O₃ nanoparticles on the non‐isothermal crystallization behaviors, crystal structure, and conductive properties of the SPE were investigated. The peak temperature, crystallinity, and crystallization half‐time (t_1/2) of the SPE were strongly dependent on the concentration of Y₂O₃ and the cooling rate. The non‐isothermal crystallization data were analyzed by the modified Avrami model, which successfully described the nonisothermal crystallization process of the SPE. The Avrami exponents suggested that the Y₂O₃ nanoparticles significantly affected both the nucleation mechanism and crystal growth of the PEO matrix. The nucleating and crystallization activation energies (ψ and E_c) estimated with different theories indicated that the Y₂O₃ nanoparticles were inclined to serve as heterogeneous nucleating agents to benefit the crystallization at lower concentration whereas as physical hindrance to inhibit the crystal growth at relatively higher concentration. The maximum conductivity (σ) of 5.95 × 10^?5 S cm^?1 at room temperature for the SPE was obtained at the Y₂O₃ weight ratio of 0.10. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Thulium Oxide Nanopowders Obtained by Precipitation

The aim of this work was to investigate the influence of precipitation parameters on the morphology of obtained thulium oxide powders. Tm₂O₃ precursor powders were synthesized by precipitation method using 0.1–0.25M water solutions of thulium nitrate and 1.5M ammonium hydrogen carbonate water solution as a precipitation agent. The processes were conducted at different temperatures (25–50°C). The result showed that the morphology of the obtained thulium oxide (Tm₂O₃) powders depends both on the molar concentration of thulium nitrate and the temperature of precipitation. Small, round, loosely agglomerated Tm₂O₃ nanoparticles were obtained after air calcination of precursor precipitated at room temperature with the use of 0.1M thulium nitrate solution.     

Ball milling assisted preparation of nano La–Y/ZrO2 powder ternary oxide system: Influence of doping amounts

Zirconia powder with good dispersion, fine particle size, and stability is used as high-quality raw material in many fields, such as ceramic materials and refractories. In this paper, the influence of lanthanum oxide (La₂O₃) and yttrium oxide (Y₂O₃) co-doped zirconia (ZrO₂) on its phase transformation behavior, phase stability, and microstructure were investigated. The ball milling method is applied to fabricate different amounts of La₂O₃-doped yttrium oxide stabilized zirconia oxide. Then, the powder obtained from ball milling was roasted using the microwave sintering method. The samples were characterized using XRD, FT-IR, Raman, SEM and BET to determine the optimal conditions for La₂O₃–Y₂O₃ co-doped ZrO₂ powder. The results showed that replacing part of Y₂O₃ with La₂O₃ increases zirconia powder's tetragonal and cubic phase, enhancing the fracture strength of the subsequent synthesized materials. At the same time, the stability of zirconia stabilized with La₂O₃ doping is significantly improved compared to that of Y₂O₃ alone. According to all analysis methods, when the doping amount is 2.8Y0.2La, the powder's phase composition, stability, particle size distribution, and dispersion degree are the best compared with other doping amounts in our study. The obtained powder has a smaller specific surface area, a lower surface energy, a smaller porosity, and a higher density. The samples under this condition can be better used in subsequent materials. The enhancement of various properties of zirconia can significantly prolong the service life of materials in practical applications.     

Optically transparent ceramics based on yttrium oxide using carbonate and alkoxy precursors

Methods for producing optically transparent ceramic materials based on Y₂O₃ using carbonate and alkoxy precursors are considered. It is established that ceramic synthesized from yttrium isopropylate has better optical parameters than ceramics based on yttrium carbonate under equal heat treatment and firing regimes. __________ Translated from Steklo i Keramika, No. 8, pp. 17–19, August, 2006.     

Comparison of the performance of copper oxide and yttrium oxide nanoparticle based hydroxylethyl cellulose electrolytes for supercapacitors

Biodegradable solid polymer electrolyte (SPE) systems composed of hydroxylethyl cellulose blended with copper(II) oxide (CuO) and yttrium(III) oxide (Y₂O₃) nanoparticles as fillers, magnesium trifluoromethane sulfonate salt, and 1‐ethyl‐3‐methylimidazolium trifluoromethane sulfonate ionic liquid were prepared, and the effects of the incorporation of CuO and Y₂O₃ nanoparticles on the performance of the SPEs for electric double‐layer capacitors (EDLCs) were compared. The X‐ray diffraction results reveal that the crystallinity of the SPE complex decreased upon inclusion of the Y₂O₃ nanoparticles compared to CuO nanoparticles; this led to a higher ionic conductivity of the Y₂O₃‐based SPE [(3.08 ± 0.01) × 10^?4 S/cm] as compared to CuO [(2.03 ± 0.01) × 10^?4 S/cm]. The EDLC performances demonstrated that the cell based on CuO nanoparticles had superior performance in terms of the specific capacitance, energy, and power density compared to the Y₂O₃‐nanoparticle‐based cell. However, Y₂O₃‐nanoparticle‐based cell displayed a high cyclic retention (91.32%) compared to the CuO‐nanoparticle‐based cell (80.46%) after 3000 charge–discharge cycles. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44636.     

Scandium ion doped yttrium oxide transparent ceramic from nitrate alanine microwave combustion synthesized nanopowders

One atomic percent Neodymium ion doped Yttrium oxide, with 25 at% scandium ion (Nd_0.02Sc_0.5Y_1.48O₃), was synthesized by nitrate alanine microwave gel combustion followed by calcinations at 1000 °C for 2 h. Phase purity of nanopowder was characterized by X-Ray Diffraction (XRD). Neodymium and scandium ion doping was confirmed by cell parameter calculation and Scanning Electron Microscope-Electron Dispersive X-ray (SEM-EDX) analysis. Particles with size range 25–35 nm with close to spherical shape were obtained as observed by Transmission Electron Microscopy (TEM). Powder on compaction followed by vacuum sintering at 1765 °C for 40 min led to the formation of ceramic with 76% transmission at 2500 nm compared to translucent ceramic obtained without scandium ion doping. This indicates formation of highly sinterable neodymium doped yttrium oxide nanopowders by nitrate alanine microwave gel combustion route with scandium ion additive. Further the absorption and emission bands of Nd_0.02Sc_0.5Y_1.48O₃ are inhomogeneously broadened and fluorescence lifetime is longer than Nd_0.02Y_1.98O₃.     

Effect of dispersion of pure yttrium oxide on its pressing and sintering

Conclusions The yttrium oxide powder has an aggregated structure: the aggregates consist of particles of different size. In order to break down the aggregation of crystals in the original Y₂O₃ it is sufficient to use shortterm grinding (6 h) with the wet method in a ball mill; this yields a powder with a high dispersion and excellent pressibility. Grinding yttrium oxide in a drum made from plastic with balls made from Y₂O₃ excludes material contamination, the balls are scarcely worn away during operation, and the grinding pick-up from the lining of the mill is slight.Specimens of yttrium oxide heat processed at 900°C and ground for 6 h have the maximum density; grinding the Y₂O₃ reduces the specific fabrication pressure.After firing at 1650°C the maximum density is recorded in specimens of Y₂O₃ ground for 6 h. The specimens made from the original Y₂O₃ of the same density were obtained only after firing at 1850°C in vacuum.Translated from Ogneupory, No. 7, pp. 22–26, July, 1973.     

Ni0.5Zn0.5Fe2O4-dispersed In2O3-spotted ZnO nanoparticles: Ammonia-source and surface and photocatalytic properties

Ammonia-source, used to attain the desired pH during synthesis, is conceived to influence the physical characteristics of ZnO-based nanomaterials, and the catalytic activity is susceptible to surface characteristics of semiconductor–photocatalyst. In this context, Ni_0.5Zn_0.5Fe₂O₄-dispersed In₂O₃-spotted ZnO nanoparticles have been obtained by using either tetramethyl ammonium hydroxide or ammonium carbonate as ammonia-source at identical pH (9) using identical quantities of the precursors following identical synthetic procedure. The nanoparticles have been characterized using energy dispersive X-ray spectroscopy, elemental mapping, selected area electron and X-ray diffractometries, transmission electron microscopy, etc. The nanoparticles obtained using ammonium carbonate possess larger (1) pore width, (2) pore volume, and (3) surface area compared with nanoparticles prepared employing tetramethyl ammonium hydroxide. Although the electrical properties of both the samples do not differ remarkably, the violet light-absorption of the sample prepared using the carbonate is slightly larger than that of the other sample. Further, the In₂O₃-spotting is slightly larger on using ammonium carbonate than using tetramethyl ammonium hydroxide. To degrade dye under visible light, the sample obtained using ammonium carbonate shows larger catalytic activity compared with nanoparticles prepared using tetramethyl ammonium hydroxide. The observed photocatalytic activities are explained based on the surface characteristics.     

Characterization of High-Gadolinium Y0.6Gd1.34Eu0.06O3 Powder and Fabrication of Transparent Ceramic Scintillator Using Pressureless Sintering

Comparatively high gadolinium contents are of primary importance for (Y,Gd)₂O₃:Eu scintillators because of expected higher scintillation intensity and higher light output of the materials. Transparent Y_0.6Gd_1.34Eu_0.06O₃ ceramic, with a high gadolinium composition of ∼67 mol%, has been fabricated via vacuum sintering using synthesized sinterable powders. The precursor powder was coprecipitated with ammonium hydrogen carbonate as the precipitant and the powder calcined at 1100°C showed the best sintering activity. Transparent Y_0.6Gd_1.34Eu_0.06O₃ ceramic, exhibiting an in-line transmittance of 66.7% at 610 nm, was obtained by vacuum sintering at 1670°C for 2 h. Under X-ray excitation, the ceramic exhibited characteristic emissions of the Eu³⁺ ions.     

Translucent yttrium oxide ceramics from low-density green bodies shaped by uniaxial pressing

Highly compact green bodies are usually required to fabricate transparent or translucent polycrystalline yttrium oxide. The present work reports on the fabrication of highly dense (ρ_rel >98%) translucent Y₂O₃ from low-density green bodies by exploiting a high sinterability of nano Y₂O₃ powder. A commercial nano Y₂O₃, with a crystallite size of ca. 30 nm, was shaped by uniaxial pressing and, afterwards, densified by pre-sintering at 1500 °C followed by hot isostatic pressing. The coarsening tendency of yttria nanoparticles causes the rearrangement of particles and results in the high sinterability of nano Y₂O₃ even at low green densities. This improves the packing density and enables sintering to high densities, eliminating pores, and, thus, obtaining translucent Y₂O₃.     

Effect of YF3 on densification behavior and thermal conductivity of AlN ceramics with Y2O3–YF3 additives under reducing atmosphere

The effect of yttrium fluoride (YF₃) on the densification behavior, microstructure, phase composition and thermal conductivity of aluminium nitride (AlN) ceramics with yttrium oxide (Y₂O₃) and YF₃ additives were studied. Since YF₃ provided liquid phases and promoted densification at a lower temperature, the sintering temperature required to reach the full density of AlN samples decreased with the increase in YF₃ content. Appropriate addition of YF₃ could improve the thermal conductivity of AlN ceramics, but the values of thermal conductivity decreased as YF₃ increased further. It is attributed to the ability of YF₃ to react with oxygen impurity was worse than that of Y₂O₃. Moreover, the reducing atmosphere significantly affected the phase composition, and the oxygen content in grain boundary phases decreased at 1750 °C and 1800 °C. Therefore, the proper proportion of Y₂O₃–YF₃ additives could simultaneously improve densification and the thermal conductivity of AlN samples at a low sintering temperature.     

Passivation effect on the surface characteristics and corrosion properties of yttrium oxide films undergoing SF6 plasma treatment

This study investigates the structures, compositions and fluorocarbon-plasma etching behaviors of yttrium oxyfluoride (YOF) passivation films fabricated on sputter-deposited yttrium oxide (Y₂O₃) by high-density SF₆ plasma irradiation. High-resolution transmission electron microscopy and nano-beam electron diffraction confirmed a YOF passivation film containing multiple phases of (104) and (006) crystal planes was formed on the fluorinated Y₂O₃ surface. X-ray photoelectron spectroscopy revealed few changes in the chemical compositions and surface roughness of the YOF passivation film after fluorocarbon plasma etching, confirming the chemical stability of the SF₆ plasma-treated Y₂O₃ sample. The etching depth was ～20% lower on the SF₆ plasma-treated Y₂O₃ film than on the commercial Y₂O₃ coating. These results showed that the SF₆ plasma-treated Y₂O₃ films have an excellent erosion resistance properties compared to the commercial Y₂O₃ coatings.     

Chemical and Textural Characterization of Iron Oxide Nanoparticles and Their Effect on the Thermal Decomposition of Ammonium Perchlorate

Metal oxide nanoparticles have been used as burning rate catalysts for ammonium perchlorate (AP) decomposition in composite solid propellants. Though most papers point to the efficiency of different sizes, shapes and compositions, the texture of the agglomerated particles plays an important role in the catalytic efficiency, but this aspect is not always discussed. In this paper, iron oxide and composite iron oxide/silica powders were synthesized in microemulsion systems and their effect on the decomposition of AP was investigated. X‐ray diffraction (XRD) analysis and Fourier transformed infrared spectroscopy (FT‐IR) showed that the synthesized powders have an amorphous to nanocrystalline pattern, with Fe₂O₃ composition. The use of different FT‐IR spectroscopic techniques – transmission, diffuse reflectance (DRIFT) and universal attenuated total reflectance (UATR) – allied to electron microscopy analysis allowed the characterization of the samples’ surface, indicating that silicon oxide forms a thick matrix that covers the iron oxide nanoparticles. Adsorption of N₂, light scattering and electron microscopy pointed that all samples are formed by mesoporous agglomerated nanoparticles containing micropores indicating that silicon oxide forms a thick matrix that covers the iron oxide nanoparticles. Adsorption of N₂, pointed that all samples show different microstructures and light scattering indicated results refer to agglomerated particles. Finally, the catalytic effect of the samples on the decomposition of AP was evaluated by thermogravimetric analysis coupled to differential thermal analysis (TG/DTA), showing that only the high temperature decomposition step of AP was affected by the catalyst, shifting to lower temperatures the higher the surface area of the synthesized iron oxide sample, regardless of the presence of the silica matrix.     

Effect of filler‐polymer interactions on the crystalline morphology of PEO‐based solid polymer electrolytes by Y2O3 nano‐fillers

A novel lithium solid polymer electrolyte (SPE) based on polyethylene oxide (PEO) matrix and yttrium oxide (Y₂O₃) as nano‐filler was prepared by solution casting technique. The Lewis acid‐based filler‐polymer coordination interactions between the surface of Y₂O₃ and the ether oxygen of PEO were proved by FTIR, which induced an obvious modification of crystalline morphology of the PEO‐based SPEs. Polarized optical microscope (POM) analysis shows that the induced nucleation and steric hindrance effects of Y₂O₃ nano‐filler result in the increased amount as well as decreased size of spherulites in the PEO matrix, respectively. Atomic force microscope (AFM) images indicate the surface morphology of PEO gets rougher as Y₂O₃ content increases. X‐ray diffractomer (XRD) and differential scanning calorimetry (DSC) results demonstrate the crystallinity of SPEs decreases from 51.1% to 32.5% with the Y₂O₃ weight ratio [m(Y₂O₃)/m(PEO+LiI)] increasing from 0 to 0.15. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Advanced high-density oxide ceramics with a controllable microstructure. Part V. Chemically stable dense ceramics based on yttrium, scandium, and aluminum oxides

Data on sintering of Y₂O₃ ceramics are presented. It is shown that the degree of sample sintering depends on the powder agglomeration, which is determined by the nature of the starting material and the conditions of Y₂O₃ production. Y₂O₃ powder produced from yttrium carbonate exhibits the best sintering characteristics. The samples thus obtained are sintered to a relative density of about 95% even at 1600°C. Dry treatment of various Y₂O₃ powders in a planetary mill equalizes their properties and reduces the sintering temperature substantially. Data on the properties of Y₂O₃ ceramics are presented. Translated from Ogneupory i Tekhnicheskaya Keramika, No. 1, pp. 2–7, January, 1997. For the beginning and continuation of the review see issues Nos. 1,2,4-7,9, and 12 of 1996.     

Effects of post-deposition annealing ambient on band alignment of RF magnetron-sputtered Y2O3 film on gallium nitride

The effects of different post-deposition annealing ambients (oxygen, argon, forming gas (95% N₂ + 5% H₂), and nitrogen) on radio frequency magnetron-sputtered yttrium oxide (Y₂O₃) films on n-type gallium nitride (GaN) substrate were studied in this work. X-ray photoelectron spectroscopy was utilized to extract the bandgap of Y₂O₃ and interfacial layer as well as establishing the energy band alignment of Y₂O₃/interfacial layer/GaN structure. Three different structures of energy band alignment were obtained, and the change of band alignment influenced leakage current density-electrical breakdown field characteristics of the samples subjected to different post-deposition annealing ambients. Of these investigated samples, ability of the sample annealed in O₂ ambient to withstand the highest electric breakdown field (approximately 6.6 MV/cm) at 10⁻⁶ A/cm² was related to the largest conduction band offset of interfacial layer/GaN (3.77 eV) and barrier height (3.72 eV).