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Frase, Katharine‐G.; Liniger, E. G.; Clarke, David R.
doi: 10.1111/j.1151-2916.1987.tb05740.xpmid: N/A
We report the compatibility relationships between compounds, including the newly discovered superconducting Y1Ba2Cu3Ox phase, in the Y2O3‐BaO‐CuO system at 950°C. In addition to the previously reported ternary compounds, there is a new compound with a composition YlBa3Cu2Ox. The new compound is a perovskite 'space group P4mm) with lattice parameters a =4.078 Å (0.4078 nm) and c =4.01 Å (0.401 nm). There are also at least two structurally distinguishable binary phases between barium oxide and the known BaCuO2, but they appear to be hygroscopic and are beyond our current capabilities of analysis.
Usha Devi, Subba Rao; Ming, Li Chung; Manghnani, Murli H.
doi: 10.1111/j.1151-2916.1987.tb05747.xpmid: N/A
The structure of CaO‐stabilized cubic zirconia has been investigated by X‐ray diffraction at high temperatures and pressures up to 1000°C and ∼35 GPa, using a diamond‐anvil cell interfaced with aYAG laser heating system. At ∼1000°C and 15 GPa, the cubic phase transforms directly into an orthorhombic phase with the PbCl2 structure. This high‐pressure phase is quenchable. The zero‐pressure lattice parameters are a=0.3327±0.0004 nm, b=0.5566±0.0003 nm, and c =0.6487±0.0005 nm, the volume change being 10.5%.
doi: 10.1111/j.1151-2916.1987.tb05743.xpmid: N/A
When the sintering of a polycrystalline body is analyzed by coupling the change in interface energies and the change in total volume of the polycrystal, it is discovered that the sintering pressure is a sum of two terms, one deriving from the surface curvature of the pores and the other depending on the size of the grains. When pores are present at two‐grain, three‐grain, or four‐grain junctions, and when the number of pores of each type per particle remains constant, the sintering pressure is expressed by a simple equation. This result may suggest new approaches to the problem of grain growth during the sintering process. The result also highlights a fundamental difference between the sintering of ceramics and the sintering of glasses.
Windisch, Charles F.; Bates, J. Lambert; Boget, Delmar I.
doi: 10.1111/j.1151-2916.1987.tb05748.xpmid: N/A
When used as components of advanced energy conversion systems, oxide ion conductors and molten electrolytes may react or decompose according to various mechanisms. Understanding these mechanisms is important in improving system performance. In situ laser Raman spectroscopy was used successfully to study the reactions between an oxide ion conductor and a molten salt. Changes in the Raman spectrum of molten Na2SO4 were observed near Y2O3‐stabilized ZrO2 electrodes when they were polarized anodically in the molten salt. These changes were interpreted to indicate the formation of yttrium sulfate complexes.
Endo, Kazuaki; Fujimoto, Kenji; Murakawa, Kyohei
doi: 10.1111/j.1151-2916.1987.tb05746.xpmid: N/A
The dielectric properties of the Ba (Co1/3 Nb2/3)O3–Ba(Zn1/3Nb2/3)O3 system were determined. Ba (Co1/3 Nb2/3)O3–Ba(Zn1/3Nb2/3)O3 has a complex perovskite structure, a high dielectric constant, a low dielectric loss, and a low temperature coefficient of the resonant frequency. A solid‐solution ceramic with 0.7Ba (Co1/3 Nb2/3)O3·0.3 Ba(Zn1/3Nb2/3)O3 has a dielectric constant of K=33.5, Q=11000 at 6.5 GHz, and a temperature coefficient of the resonant frequency of τf=0 ppm/°C. The temperature coefficient of resonant frequency can be varied by changing the composition. The Q values of the ceramics can be increased by annealing in a nitrogen atmosphere. These ceramics can be used for resonant elements and stabilized oscillators.
Yamada, Osamu; Miyamoto, Yoshinari; Koizumi, Mitsue
doi: 10.1111/j.1151-2916.1987.tb05741.xpmid: N/A
A high‐pressure self‐combusiton sintering process has been applied to the synthesis and simultaneous sintering of titanium carbide. A dense titanium carbide compact was easily fabricated from the constituent elements without sintering aids under 3 GPa. The compact was composed of well‐crystallized grains with a mean diameter of 20 μm at a molar ratio of C/Ti =0.95. The maximum values of the relative density and the Vickers microhardness were 96.5% and 31 GN/m2, respectively, at room temperature.
Ho, William W.; Morgan, Peter E. D.
doi: 10.1111/j.1151-2916.1987.tb05742.xpmid: N/A
Rapidly increasing dielectric loss values, coinci nt with the formation, with increasing temperature, of small amounts of liquid phase, have been seen in an alumina doped with titania and soda (Al2O3‐l molc TiO2‐0.5 mol% NaO12). The method appears to have the sensitivity to detect liquids in ceramics down to 0.1% in favorable cases.
Suzuki, Suguru; Takahashi, Minoru; Hikich, Yasio
doi: 10.1111/j.1151-2916.1987.tb05745.xpmid: N/A
The free‐volume fraction (Vf) defined by Simha and Boyer was measured for network‐forming oxide glasses in the systems P2O5‐(GeO2, TeO2,Sb2O3.V2O5). The Vf values varied from 0.06 to 0.25. The systems P2O5‐TeO2: and P2O5‐Sb2O3 have Vf∼0.1, which is near the magnitude of the free‐volume fraction for normal metaphosphate glasses and many organic high polymers.
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