Papers by Keyword: Y₂O₃

Abstract: The effect of MgO-Y₂O₃ additives on densification, microstructure and mechanical properties of hot-pressed Al₂O₃-TiCN composites was studied. The MgO-Y₂O₃ additions had little influence on densification of Al₂O₃-TiCN composites. The Al₂O₃-TiCN composites without additives had coarsening microstructure, whereas that containing 0.25wt%MgO-0.5wt%Y₂O₃ had a noticeable finer microstructure and good mechanical properties. The increase of fracture toughness were attributed to the addition of MgO and Y₂O₃ together with the TiCN particles to inhibit the abnormal grain growth of Al₂O₃.

Abstract: Uniform Y₂O₃ hollow microspheres have been successfully prepared via a urea-based homogeneous precipitation technique with colloidal carbon spheres as template followed by a subsequent calcination process. The template can be effectively removed and the amorphous precursor has converted to crystalline Y₂O₃ during the annealing process. SEM images indicate that the hollow spheres inherit the spherical shape and good dispersion of the templates, and the shell of the hollow spheres is composed of a large amount of uniform nanoparticles. The lanthanide activator ion Ln³⁺-doped Y₂O₃ hollow microspheres exhibit bright upconversion luminescence with different colors under 980 nm light excitation, which may find potential applications in the fields such as light phosphor powders, advanced flat panel displays, or drug delivery.

Abstract: In this work, effects of post-deposition annealing (PDA) time (15, 30, and 45 min) in nitrous oxide ambient on Y₂O₃ film deposited on Si substrate using RF-magnetron sputtering have been systematically studied. Y₂O₃/Si system subjected to PDA time at 15 and 30 min has demonstrated a negative flatband voltage shift but a change to positive flatband voltage shift was observed when PDA time was prolonged to 45 min. The shift from negative to positive flatband voltage with enhancement of PDA time could be related to the accumulation of nitrogen in the Y₂O₃ gate that acted as negatively trap charge. It was perceived that sample subjected to PDA time at 30 min has demonstrated the best leakage current density-breakdown voltage (J-V_B) characteristic. A correlation between the J-V_B characteristics with effective oxide charge, slow trap density, interface trap density, and total interface trap density has been discussed.

Abstract: Spherical submicron SiO₂ particles have been coated with luminescent Y₂O₃: Tb³⁺ layers by a Pechini sol-gel process, resulting in the formation of SiO₂@Y₂O₃: Tb³⁺ core-shell particles. The obtained core–shell phosphors have perfect spherical shape with narrow size distribution (average size ca. 450 nm), smooth surface and non-agglomeration. The thickness of shells could be easily controlled by changing the number of deposition cycles (35 nm for two deposition cycles). Under the excitation of ultraviolet, the Tb³⁺ ion mainly shows its characteristic emissions in the core-shell particles from Y₂O₃: Tb³⁺) shells. The emission intensity of Tb³⁺ can be tuned by the annealing temperature and the number of coating cycles.

Abstract: Through a conventional ceramic process, Y₂O₃ and Sb₂O₃ co-doped ZnO-based varistors were prepared. The microstructure and electrical properties of the as-prepared varistors were investigated. Y₂O₃ could act as an inhibitor to the growth of ZnO grains when working with Sb₂O₃. The mean size of ZnO grains in the Sb₂O₃ and Y₂O₃ co-doped samples was smaller than those of the samples only added with Y₂O₃ or Sb₂O₃. And with appropriately increased ratio of Y:Sb, it would result in increased sample densification. When the doping level of Y₂O₃ was small, the nonlinear coefficient and breakdown voltage of the varistors would increase with increasing doping amounts of Y₂O₃, and the leakage current would decrease. However, when Y₂O₃ was doped without Sb₂O₃, both the nonlinear coefficient and breakdown voltage of the varistors would decrease sharply, thus the leakage current increase dramatically. The electrical properties of the Sb₂O₃ and Y₂O₃ co-doped varistors would be better than those of the samples only added with Y₂O₃ or Sb₂O₃, and when the Y:Sb atom ratio was 5, the nonlinear coefficients, breakdown voltages and leakage current of the varistors reached their optimum values of 777 V/mm, 23 and 0.17 mA/cm², respectively.

Abstract: The reaction process of synthesis of Al₄SiC₄ from Al, Si and graphite powders and the effects of Y₂O₃ on synthesis and microstructure of Al₄SiC₄ were investigated in this paper. The results show that no substantial changes in the formation of Al₄SiC₄ content with or without addition of Y₂O₃. The addition of Y₂O₃ to Al, Si and carbon powder mixtures was found to be effective for obtaining tabular grains of Al₄SiC₄. Conversely, Al₄SiC₄ grains existed as irregular granules without addition of Y₂O₃.

Abstract: Al2O3-MgO, Al2O3-Y2O3 and Al2O3-MgO-Y2O3 composite ceramics were fabricated respectively by hot-press sintering technique. With the analysis of the mechanical properties and microstructure, it was found that single additive MgO could be more favorable to the grains’ refinement and densification than Y2O3; the composite additive including both MgO and Y2O3 was better than single additive MgO or Y2O3, because their interactions could improve the mechanical properties of the Al2O3 ceramics; The sintering temperature could be reduced by adding the suitable amount of composite additives.

Abstract: In this research, the Y₂O₃ layer is doped with the zirconium through co-sputtering and rapid thermal annealing (RTA) at 550°C, 700°C, and 850°C. Then the Al electrode is deposited to generate two kinds of structures, Al/ZrN/ Y₂O₃/ Y₂O₃+Zr/p-Si and Al/ZrN/ Y₂O₃+Zr/ Y₂O₃/p-Si. According to the XRD results, when Zr was doped on the upper layer, the crystallization phenomenon was more significant than Zr was at the bottom layer, meaning that Zr may influence the diffusion of the oxygen. The AFM also shows that the surface roughness of Zr has worse performance. For the electrical property, the influence to overall leakage current is increased because the equivalent oxide thickness (EOT) is thinner.

Abstract: Fine yttrium stearate powder was produced at a relatively low temperature using yttrium nitrate hexahydrate, ammonia and stearic acid as the raw materials. Dispersed Y₂O₃ nanopowder was synthesized by calcining the yttrium stearate. The formation mechanism of the precursor and the Y₂O₃ nanopowder was studied by means of XRD, TG-DTA, FT-IR, BET, FE-SEM and HR-TEM. Pure and dispersed Y₂O₃ nanopowder with an average particle size of 30 nm was produced by calcining the precursor at 600 °C. The particle size increases to about 60 nm with the increase of the calcination temperature to 1000 °C. In the preparation of Y₂O₃ from yttrium stearate, no water medium is involved, thus capillarity force and bridging of adjacent particles by hydrogen bonds can be avoided, resulting in good dispersion of the particles. The dispersed Y₂O₃ nanopowder prepared in this work has potential application in phosphors and transparent ceramic materials.

Abstract: Nano-sized Y2O3 particles were codeposited with nickel by pulse current electroplating from a nickel sulfate bath. The effects of Y2O3 concentration in the plating bath on the deposition behaviors and mechanical properties of Ni-Y2O3 composite coatings were studied. The incorporated Y2O3 increases from 2.6 wt.% to 6.0 wt.% with the increasing of Y2O3 concentration in the plating bath from 20 to 80 g/l. The current efficiency decreases from 81.3% to 45.4% with the Y2O3 concentration increasing from 20 to 80 g/l. SEM images demonstrate that smooth and compact surface can be obtained by the addition of Y2O3. The present study also shows that the codeposited Y2O3 particles in deposits decrease the friction coefficient and reduce the wear weight loss. Ni-Y2O3 composite coating reaches its highest microhardness and best wear resistance at Y2O3 content 6.0 wt.%.