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1.
The ionic conduction in sintered oxides of the system Bi2O3-WO3 was investigated by measuring conductivities and ion transference numbers under various conditions. The ion transference number was measured by an oxygen concentration cell employing the specimen tablet as the electrolyte.It was found that a compound 3Bi2O3 WO3 and its solid solution were high oxide ion conductors, the conductivities of which were about one order of magnitude higher than those of the well-known oxide ion conductors such as stabilized zirconias. In contrast to pure Bi2O3 which is a completely electronic conductor below 730°C, these materials showed high oxide ion conduction even below 700°C accompanied by little electronic conduction. 3Bi2O3 WO3 has the face centered cubic structure, probably of the fluorite type, and the oxide ion conduction was thought to be attributed to the migration of oxide ion vacancies in the crystal. 相似文献
2.
In order to characterize the conduction behaviour in the sintered oxides of the system Bi2O2-Gd2O3, the electrical conductivity in air and the emf of the oxygen concentration cell were measured. The new rhombohedral phase found in this system exhibited high oxide ion conduction especially at relatively high oxygen pressure. The rhombohedral phase was stable in the composition range between 10 and 30 mol% Gd2O3 below 600° C and was transformed into the face-centred cubic phase with rising temperature, the conduction in which was by oxide ion as in the rhombohedral phase. At concentrations greater than 35 mol% Gd2O3, the fcc phase was stable over a wide range of temperature (~900° C) and kept its high oxide ion conduction. The conductivities of rhombohedral (Bi2O3)0.90(Gd2O3)0.10 and fcc (Bi2O3)0.65(Gd2O3) 0.35 * are 4.5 and 2.4×10?2 cm?1 at 600°C, respectively. These are about one order of magnitude higher than that of the well-known yttria-stabilized zirconia at corresponding temperatures. High-oxide ion-conduction in the rhombohedral and fcc phase was considered to be due to the appreciable numbers of oxide ion vacancies in these crystals. 相似文献
3.
The phase diagram of the Bi2O3-Er2O3 system was investigated. A monophasic f c c structure was stabilized for samples containing 17.5–45.5 mol% Er2O3. Above and below this concentration range polyphasic regions appear. The f c c phase showed high oxygen ion conduction. The ionic transference number is equal to one for specimens containing 30 mol% Er2O3 or less, while an electronic component is introduced at low temperatures for specimens containing 40–60 mol% Er2O3. Between 673 K and 873 K a maximum in the conductivity was found at 20 mol% Er2O3. (Bi2O3)0.8.(Er2O3)0.20 is found to be the best oxygen ion conductor so far known. The conductivity at 773 K and 973 K is 2.3 –1m–1 and 37 –1 m–1 respectively. These values are 2–3 times higher than the best oxygen ion conductor reported for substituted Bi2O3 systems and 50–100 times higher than those of stabilized zirconia (ZrO2)0.915(Y2O3)0.085 at corresponding temperatures. 相似文献
4.
In order to examine the conduction behaviour in the sintered oxides of MoO3-doped Bi2O3, the electrical conductivity in air and the EMF of oxygen gas concentration cell were measured with respect to the phase relation determined by X-ray diffraction.The tetragonal single phase oxide containing 22 mol% MoO3 was found to be a high oxide ion conductor, the conductivity of which was comparable to those of stabilized zirconias. The partial electronic conduction in this phase was negligibly small at relatively high oxygen pressure. The oxide ion conduction was considered to be attributable to an appreciable amount of oxygen vacancies present in the crystal. In the monoclinic compound 3Bi2O3·2MoO3, the oxide ion conduction was also observed. Although the conductivity of this phase was somewhat lower than that of the tetragonal phase, the activation energy for conduction (53·5 kJ mol–1) was much lower than the values for usual oxide ion conductors. 相似文献
5.
Ionic conduction in sintered oxides of the system Bi2O3-SrO was investigated by measuring the conductivity and ion transference number under various conditions. The ion transference numbers were measured by an oxygen concentration cell employing the specimen as the electrolyte.It was found that the solid solution containing 2040 mole% SrO which had a rhombohedral structure was an almost pure oxide ion conductor under a relatively high partial pressure of oxygen, and that the conductivity was several times higher than that of stabilized zirconias at the same temperatures up to 800°C. Oxide ion conduction was confirmed also by quantitative determination of generated O2 from the anode of the oxygen concentration cell during discharge.The sintered specimens of the systems Bi2O3-CaO and Bi2O3-La2O3 were found also to be oxide ion conductors, and the ion transference numbers were greater than 0.9. 相似文献
6.
Oxide ion and electron conduction in sintered oxides of the system Bi2O3-Pr6O11 have been studied. Two types of rhombohedral phase are formed in this system. Oxide ion conduction is predominant in the rhombohedral-phase present in the composition range less than 35 mol% Pr2O11/3. Electronic (hole) conduction appeared in addition to oxide ion conduction in another rhombohedral phase containing more than 40 mol% Pr2O11/3. This phase is of the LaOF-type which is a distorted defect fluoritetype structure. Electronic conduction in the LaOF-type phase is considered to be due to the change of oxidation state of praseodymium at high temperatures. 相似文献
7.
The cathodic current blackening of Bi2O3-based oxide ion conductors was examined for the Bi2O3-Y2O3 electrolyte at low oxygen pressure. In air, more than 500 mA cm–2 d.c. could be passed at 600° C without causing changes in the electrolyte itself. However, in argon gas, a limiting current of 3 mA cm–2 was observed and the electrolyte was blackened at the cathode side. The limiting current was ascribed to control by the diffusion of oxygen gas at the cathode. The blackened oxide was found to consist of a mixture of Bi metal and Bi2O3-Y2O3 solid solution and to exhibit the equilibrium oxygen partial pressure almost corresponding to that of the Bi, Bi2O3 mixture. 相似文献
8.
《Journal of the European Ceramic Society》2000,20(5):625-630
Ceramic compacts in the systems Al2O3–Y2O3, Cr2O3–Y2O3 and Y3(CryAl1-y)5O12 (Cr-doped YAG) were prepared by solid state reaction in calcined co-precipitated powder mixtures of appropriate compositions. Various solid-solution phases were formed, e.g. Y3(Al1-xCrx)5O12, YAlyCr1-yO3 and Al2-xCrxO3. Composite materials in the pseudo-binary or ternary systems Al2O3–Y3Al5O12, Cr2O3–Y2O3 and Y3(Al1–xCrx)5O12–YAlyCr1–yO3–(AlzCr1−z)2O3 were obtained by hot-pressing appropriate powder precursors at 1600–1650°C for 1 h. The microstructure of the prepared materials was studied in a scanning electron microscope with element analysis facilities. X-ray diffraction was used to reveal the phases present and their lattice parameters. The chemical compatibility of these phases was investigated. The results are discussed with a special emphasis on the solubility of Cr in the YAG structure, and on the compatibility relationship between Cr-doped YAG and its neighbouring phases. A gel-coating process for preparing Al2O3–YAG composites with tailored microstructures is also described. 相似文献
9.
Electrical conduction in sintered oxides of the system Bi2O3-Tb2O3.5 has been investigated. Oxide ion conduction was observed in the rhombohedral (low temperature) phase and the f c c (high temperature) phase present in the composition range less than 20mol% Tb2O3.5. The fcc phase could be stabilized at lower temperatures by adding more than 30 mol % Tb2O3.5. In addition to oxide ion conduction, appreciable electronic conduction appeared in this composition range. The oxide ion transport number of this phase decreased with increasing content of Tb2O3.5 and the specimens having 40–50 mol % Tb2O3.5 showed mixed conduction where electrical conduction was comparably contributed by oxide ions and electrons. Electronic conduction in the fee phase was considered to be due to the change in valence of terbium at high temperatures. 相似文献
10.
V. N. Strekalovskii é. G. Vovkotrub A. I. Lipchak S. G. Mikhailov V. I. Solomonov 《Refractories and Industrial Ceramics》1999,40(1-2):51-55
The method of pulse high-current cathode luminescence is used to study the Bi2O3-Er2O3-CeO2 system at room temperature in air. New luminescence centers associated presumably with cation vacancies and an anion vacancy
are determined in systems containing CeO2. The luminescence parameters are shown to behave nonmonotonically with variation of the composition of the system. It is
assumed that an abrupt change in these parameters at a certain composition of the substance corresponds to a phase transformation. 相似文献
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13.
E. S. Lukin A. S. Vlasov N. M. Astakhova E. V. Bykova 《Refractories and Industrial Ceramics》1987,28(1-2):63-65
Conclusions A highly dense ceramic based on the eutectic composition of the Al2O3-ZrO2 system was obtained using 3 mole % Y2O3 addition. The ceramic has a fine-grained structure and high hardness and strength.Translated from Ogneupory, No. 2, pp. 8–10, February, 1987. 相似文献
14.
采用Nb2O3、Y2O3复合稳定剂,制得了高韧性、高强度的四方相ZrO2陶瓷材料,发现在Y2O3-ZrO2材料中加入0.5-1molNb2O3,可使材料在保持原有抗弯强度的同时,一定程度上改善了断裂韧性和相组成。 相似文献
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16.
LaOF-type tetragonal solid solution was found in the system La2O3–MgF2. This phase showed higher anionic conduction than the previously reported cubic solid solution in the system La2O3–CaF2. Electrolysis by Tubandt's method showed that fluoride ion conduction was dominant in this solid solution. The fluoride ions were considered to be easily substituted by oxide ions through cathode reaction in the oxygen atmosphere. 相似文献
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18.
《Ceramics International》2017,43(6):4930-4936
A complete subsolidus ternary phase diagram of the Bi2O3-CuO-Nb2O5 (BCN) system was constructed. Careful firing control and phase analysis were applied to determine the phase assemblages and compatibilities over a wide range of temperatures, i.e. 700–925 °C. Phase-pure BCN pyrochlores were found to crystallise in cubic symmetry, space group Fd3m, No. 227 with lattice constants in the range of 10.4855 (5)<x<10.5321 (3). The mechanism of this limited subsolidus series could be represented by a general formula, Bi3.08−xCu1.84+2x/9Nb3.08+7x/9O14.16+6x/9 (0≤x≤0.36) wherein the reduction in Bi content was compensated by a proportion amount of copper and niobium together with non-stoichiometry in oxygen. 相似文献
19.
The processes of film formation in a ternary system are studied, beginning with the preparation of the working solution and up to coat firing. It is demonstrated that the properties and quality of a coating are determined at the stage of preparing a film-forming solution and depend on the size and shape of the sol particles, the film porosity, and the diffusion process at the glass-film interface. 相似文献
20.
《Ceramics International》2020,46(1):487-492
Bi2O3 and Al2O3 were proven to separately have an impact on grain growth of LiZn ferrite ceramics. In this study, we synthesized LiZnTiMn ferrite ceramics under low temperature (<920 °C) using rationally designed formula of Bi2O3-Al2O3 as sintering agents. Microstructures, densities, and ferromagnetic performances were systematically investigated. Results show that appropriate amount of Bi2O3-Al2O3 leads to successful sintering of LiZnTiMn ferrites even below 900 °C. X-Ray diffraction (XRD) and scanning electron microscopy (SEM) results show that spinel structure ferrite ceramics were obtained and that the addition of Bi2O3-Al2O3 accelerated solid-state reaction. Corresponding ferromagnetic properties, including saturation induction (Bs), remanence square ratio, coercivity (Hc), ferromagnetic resonance linewidth (ΔH), and Ms, were also investigated. At 920 °C, with addition amount of x=1 wt%, we obtain excellent performance: Bs=306 mT, Br/Bs=0.849, Hc=2.34Oe, and ΔH=275 Oe. Results indicate that Bi2O3-Al2O3 is promising sintering agent for low-temperature sintering of LiZnTiMn ferrite ceramics. 相似文献