Hot corrosion behaviors of SrZrO3 ceramic co-doped with Y2O3 and Yb2O3 in molten Na2SO4, V2O5, and Na2SO4 + V2O5 salts mixture

The hot corrosion behaviors of Sr(Y_0.05Yb_0.05Zr_0.9)O_2.95 (SYYZ) ceramic were investigated in Na₂SO₄, V₂O₅, and Na₂SO₄ + V₂O₅ salts mixture, respectively. Na₂SO₄ did not react with SYYZ ceramic at 900, 950 and 1000 °C. m-ZrO₂, YVO₄ and YbVO₄ were the main corrosion products on the SYYZ ceramic surface in V₂O₅ at 800 and 900 °C, whereas Sr₃V₂O₈ and t-ZrO₂ appeared at 1000 °C. In Na₂SO₄ + V₂O₅ salts mixture, the corrosion products were Sr₃V₂O₈ and t-ZrO₂ at 800 and 900 °C on the SYYZ ceramic surface, however, a new phase of SrZrO₃ developed at 1000 °C. The phase transformation and chemical interaction are the primary corrosion mechanisms for degradation of SYYZ ceramic.     

B2O3-La2O3-Ta2O5-ZrO2系统中新型ZLaF4玻璃的研制

研究了B2O3含量为20%(质量分数)时B2O3-La2O3-Ta2O5-ZrO2和B2O3-La2O3-Nb2O5-ZrO2系统的玻璃形成区域.在此基础上,逐一添加各种改善析晶性能的氧化物,研制出一种高折射率低色散的ZLaF4光学玻璃,并对其熔炼工艺、析晶性能作了一定的探讨,对一些性能进行了测试.     

Thermal and optical properties of La2O3–Ga2O3– (Nb2O5 or Ta2O5) ternary glasses

La₂O₃–Ga₂O₃–M₂O₅ (M = Nb or Ta) ternary glasses were fabricated using an aerodynamic levitation technique, and their glass‐forming regions and thermal and optical properties were investigated. Incorporation of adequate amounts of Nb₂O₅ and Ta₂O₅ drastically improved the thermal stabilities of the glasses against crystallization. Optical transmittance measurements revealed that all the glasses were transparent over a wide wavelength range from the ultraviolet to the mid‐infrared. The refractive indices of the glasses increased and the Abbe number decreased upon substituting Ga₂O₃ with Nb₂O₅, and the decrease in the Abbe number was significantly suppressed when Ta₂O₅ was incorporated into the glass. As a result, excellent compatibility between high refractive index and lower wavelength dispersion was realized in La₂O₃–Ga₂O₃–Ta₂O₅ glasses. Analysis based on the single‐oscillator Drude–Voigt model provided more systematical information and revealed that this compatibility was due to an increase in the electron density of the glass.     

Metastability in the MgAl2O4–Al2O3 System

Aluminum oxide must take a spinel form (γ‐Al₂O₃) at increased temperatures in order for extensive solid solution to form between MgAl₂O₄ and α‐Al₂O₃. The solvus line between MgAl₂O₄ and Al₂O₃ has been defined at 79.6 wt% Al₂O₃ at 1500°C, 83.0 wt% Al₂O₃ at 1600°C, and 86.5 wt% Al₂O₃ at 1700°C. A metastable region has been defined at temperatures up to 1700°C which could have significant implications for material processing and properties. Additionally, initial processing could have major implications on final chemistry.     

Aerosol Codeposition of Ceramics: Mixtures of Bi2O3–TiO2 and Bi2O3–V2O5

Aerosol deposition (AD) is a promising method to apply ceramic films on a wide range of substrate materials. Until now, AD has mainly been performed using a single ceramic powder. In this work, mixtures of two different ceramic powders were prepared. The first mixture consisted of Bi₂O₃ and TiO₂ and the second consisted of Bi₂O₃ and V₂O₅, in stoichiometric ratios to form Bi₄Ti₃O₁₂ and Bi₄V₂O_11?δ, respectively. Aerosol codeposition produced films with homogeneously distributed particle fractions and thicknesses between 10 and 100 μm. Composite films were annealed to temperatures up to 750°C to enable an in situ calcination and attempted formation of the above‐mentioned compounds. Successful formation of Bi₄Ti₃O₁₂ was tracked by hot‐stage X‐ray diffraction (XRD), and confirmed by dielectric measurements. Formation of the intended Bi₄V₂O_11?δ, on the other hand, was not achieved, but rather BiVO₄, which was confirmed by XRD, EDX and electrical measurements. The bismuth deficiency occurred during spray deposition, and is attributed to powder/material characteristics. Additional insight about the AD process is gained by comparing mixtures of oxides with different relative hardness values. Aerosol codeposition of ceramics may be an interesting new technique for producing porous functional ceramics.     

N2O4-N2O5- HNO3体系液液平衡数据测定

采用浊点法测定了N2O4-N2O5-HNO3体系在258.2～281.2 K的液液平衡和固液平衡数据,得到了固液平衡临界点及N2O5在N2O4和HNO3中的溶解度、N2O4在HNO3中的溶解度和HNO3在N2O4中的溶解度数据,确定了液液平衡区域和近似固液平衡区域.结果表明,随着温度的升高,两相区逐渐减小;N2O5在N2O4和HNO3中的溶解度、N2O4在HNO3中的溶解度和HNO3在N2O4中的溶解度均增大.     

(Sb2O3/Sb2O5)-doped SnO2–Co3O4–Cr2O3 varistors: The Sb2O4 in-situ formation and its influence over the electrical and microstructural properties

The present study aimed to systematically study the transitions and consequential effects of antimony oxide (Sb₂O₃ or Sb₂O₅) additions over the properties of a SnO₂-based varistor system. High energy ball-milling and conventional sintering were used to obtain the samples with the following molar composition: (98.95-X)% SnO₂ - 1% Co₃O₄ - 0.05% Cr₂O₃ - X% Sb₂O₃/Sb₂O₅ where X = 0, 0.05, 0.1, 0.2 and 0.4 mol%. The thermal analysis suggested the in-situ formation of Sb₂O₄ at ~450 °C from Sb₂O₃ or Sb₂O₅ during the sintering of mixed oxides. SEM, XRD, and electrical analysis revealed similar results by using Sb₂O₃ or Sb₂O₅; the addition of 0.05 mol% antimony oxide provides the foremost properties. The transition equations from Sb₂O₃ or Sb₂O₅ to Sb₂O₄ demonstrate equivalency in the amount of Sb₂O₄ formed. That fact, besides the results obtained, were used to discuss a reasonable route for Sb³⁺ and Sb⁵⁺ incorporation within the SnO₂ lattice.     

Core–Shell Structure and Dielectric Properties of Ba0.991Bi0.006TiO3@Nb2O5–Co3O4 Ceramics

To meet the needs of future multilayer ceramic capacitors (MLCCs), thinner dielectric layers are necessary. To achieve this goal, the grain size and uniformity of the particles must be effectively controlled. In this study, we confirmed a core–shell particle structure by means of X‐ray diffraction, scanning electron microscopy, and energy‐dispersive spectroscopy. The dielectric properties of the ceramics were measured using an LCR meter. We found Ba_0.991Bi_0.006TiO₃ particles form a core that was coated with a homogeneous Nb₂O₅–Co₃O₄ layer (~9 nm). The relationship between core–shell structure and ε_r‐T curves of the Ba_0.991Bi_0.006TiO₃@Nb₂O₅–Co₃O₄ ceramics by different sintering temperature has been investigated. Dense, fine‐grained Ba_0.991Bi_0.006TiO@Nb₂O₅–Co₃O₄ ceramics were obtained by sintering at 1160°C. The ceramics met the X8R requirements, with a maximum dielectric constant of 2795, and a low dielectric loss at room temperature of 0.89%.     

Phase equilibrium studies in V2O5-Fe2O3 and V2O5-TiO2 systems

V₂O₅-Fe₂O₃ and V₂O₅-TiO₂ systems represent two important chemical systems with various applications, including energy, catalysts, and high-performance materials. In the present study, high-temperature phase equilibrium experiments were conducted at the temperature range of 670–1000°C in air. Electron probe X-ray micro-analyzer (EPMA) was used to analyze the microstructure and composition of the phases presented in quenched samples. Systematic experiments demonstrated that V₂O₅-containing systems should not be quenched by water-based quenching media. Phase diagrams in both systems were constructed, and the eutectic and peritectic points of the systems were confirmed and compared with previous studies. The present study improved the previous results and could be used as the base for thermodynamic modelings and further applications of the two systems.