Hexagonal yttrium manganite:A review on synthesis methods,physical properties and applications

Hexagonal rare-earth manganites have attracted considerable interest due to their complex multiferroic properties,and they possess a spontaneous electric polarization and may be utilized in various technological applications ranging from solar cells to non-volatile memories and light polarizers.The narrow bandgap of hexagonal rare-earth manganite-based compounds can perform remarkable optical anisotropy properties,which make these very efficient photovoltaic materials in parallel with the widely...     

Effect of Y2O3 content on densification,microstructure and mechanical properties of reaction sintered magnesium aluminate spinel

Dense magnesium aluminate (MgAl₂O₄) spinels were developed via single-stage solid-state reaction sintering method at 1550–1650^oC using combinations of varied commercial grade reactants-three different sources of alumina and two different sources of magnesia. The effect of Y₂O₃ doping in the concentration range of 1–4 wt % on different spinel batches was studied. Y₂O₃ addition was found to favour the densification of all the spinels at all dopant concentrations and maximum densification was found for the 2 wt % Y₂O₃ containing spinel batches. Phase analysis of the Y₂O₃ containing batches revealed the presence of yttrium aluminum garnet (YAG, Y₃Al₅O₁₂) at all the sintering temperatures. Owing to similar crystal structure isotropic configuration of YAG (cubic) as that of spinel (cubic), Y₂O₃ doping was found to favour densification of spinel. Microstructural investigation revealed that Y₂O₃ containing batches have a controlled grain structure as compared to the without additive batches. Also, 2 wt % Y₂O₃ containing spinel batches sintered at 1650^oC revealed better mechanical properties such as cold modulus of rupture and strength retainment after thermal shock than that of the undoped spinel batches.     

Chemical interaction of Y2O3 coating with U-Zr-Nd metallic fuel during casting

The interaction between molten metals and ceramic coating materials was studied to minimize fuel material loss and develop a reusable crucible for fuel melts. U-Zr-Nd alloy and pure Nd were used as metal melts while the substrate pellets were Y₂O₃-plasma-spray-coated graphite. The metals were melted using the sessile drop test method on Y₂O₃-coated graphite pellets. All Y₂O₃ coating layers of the specimens detached from the graphite specimens and attached to the molten metals because of their reactivity. Furthermore, a microstructural analysis of the specimens was performed after droplet testing. The results revealed that (Nd,Y)₂O₃ compounds were formed by the reaction between Nd and Y₂O₃ coating during the U-Zr-Nd fuel melting on the substrate.     

Ethanol-induced formation of precursor for 8 mol% Yttria-stabilized zirconia: Towards the production of well-dispersed,easily sintering,and high-conductivity nano-powders

This study aims to prepare novel precursor powders for 8 mol% yttria-stabilized zirconia nano-powders. Precursor powders were extracted from the ethanol-water solution, which utilizes the changing solvation energy for different ions impacted by ethanol. An aqueous solution containing zirconium sulfate tetrahydrate and yttrium sulfate octahydrate was mixed with different volumes of ethanol to prepare precursor powders, then calcinating to obtain 8 mol% yttria-stabilized zirconia nano-powders. The scanning electron microscope and particle size measurements for precursor powders suggested that the ideal volume ratio between ethanol and the aqueous solution was 2.5, corresponding to the complete precipitation and well-dispersion. The X-ray diffraction measurements, crystallization kinetics calculations, and scanning electron microscope after calcinating precursor powders indicated the successful formation of 8 mol% yttria-stabilized zirconia powders and the particle growth through a one-dimensional growth mechanism in the 60–120 nm size range. The densification experiments and electrochemical performance measurements after sintering 8YSZ nano-powders showed high density and high ionic conductivity compared with commercial powders. An efficient process, successfully designed to achieve the commercial requirement, was used to prepare 8YSZ nano-powders.     

Effect of yttrium (Y) substitution on the structure and dielectric properties of BaTiO3

As the rate of application of multilayer ceramic capacitors (MLCCs) in small electronic devices increases, the use of the raw material barium titanate (BaTiO₃) with a small particle size and excellent dielectric properties becomes needed. Due to the size effect, small-sized BaTiO₃ generally has a cubic phase structure with a low dielectric constant, which limits its use in MLCCs. We report the preparation of small cubic phase Y-doped BaTiO₃ (BYT) nanoparticles by a hydrothermal method and the preparation of highly dielectric tetragonal phase BYT ceramics based on this method. XRD and Raman analysis showed that the BYT nanoparticles are in substable cubic phases. The particle size of the BYT nanoparticles, measured by TEM, XRD, and BET, was approximately 35 nm. The dielectric properties of the BYT ceramics were tested by an impedance analyzer, and the dielectric constant of the BYT ceramics was 7547 when the Y³⁺ doping amount was 0.5 mol%. In addition, the substitution mechanism of Y³⁺ doping in BaTiO₃ crystals was proposed from XPS and EPR analysis. The results demonstrate for the first time that the 50 nm cubic phase BaTiO₃ powder can meet the needs of next-generation high-capacity MLCCs. This work provides a reference for small cubic phase BaTiO₃ as a dielectric material for high-capacity MLCCs.     

Evolution and effect on electrolysis performance of pores in YSZ electrolyte films prepared by screen-printing

Insights into the pore–matrix interactions in solid oxide electrolytes are necessary to develop high-efficiency solid oxide electrolytic cells. The role of particle size in ink and printed electrolyte films was analyzed in this study. This is distinct from solid electrolytes that are dense as a whole but have micropores. Herein, we demonstrate that the organic binder in the ink can significantly reduce the number of closed pores in the electrolyte by taking advantage of its thermal softening characteristics. Electron microscopic analysis provides evidence that the binder controls the pore generation and affects the pore distribution in the electrolyte films. The effect and mechanism of micropores in the electrolyte on the electrochemical process (when used for high-temperature steam electrolysis) are discussed.     

Y对新型Fe-Ni-Cr-Al合金高温氧化行为的影响

利用恒温氧化试验研究了不同Y含量的新型Fe-Ni-Cr-Al合金在1300℃空气中的氧化行为，采用X射线衍射仪器（XRD）和扫描电子显微镜（SEM）研究了氧化产物类型和分布。结果发现Y的添加有益于提高Fe-Ni-Cr-Al合金的抗氧化能力，其原因是Y元素的添加促进了Fe-Ni-Cr-Al合金表面形成致密的尖晶石和氧化铬的复合保护层，减缓了基体合金元素的扩散，同时，Y的加入促进了Al2O3由内氧化向外氧化的转变，减缓了合金内氮化进程，整体提高了合金的抗氧化性能。     

Heterogeneous microstructure of yttrium hydride and its relation to mechanical properties

The goal of this study is to investigate the properties of yttrium hydride materials in relation to the microstructure, especially its homogeneity. High-throughput nanoindentation mapping was used to evaluate hardness distribution. Raman spectral imaging demonstrated its sensitivity to the presence of YH2 and impurities. Raman peak position maps were correlated with residual stress in the specimens. Electron backscatter diffraction mapping provided phase distributions with correlation to high-energy X-ray diffraction analysis. The experimental mapping data were combined and analyzed using unsupervised machine learning cluster procedures. The machine learning analysis revealed that yttrium hydride specimens contained a major δ-YH2 − x phase component and minor α-Y and δ-YH2 − x components with significant residual stress. The minor phase fraction decreased with increasing nominal H/Y ratio, which affected the nanoindentation and Vickers hardness. The multimodal mapping procedures described herein affect developing important microstructure–property relationships, as well as correlations in heterogeneity and mechanical properties.