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1.
MASARU MIYAYAMA SHINICHI KATSUTA YOSHIHIRO SUENAGA HIROAKI YANAGIDA 《Journal of the American Ceramic Society》1983,66(8):585-588
Electrical conduction in tetragonal β-Bi2 O3 doped with Sb2 O3 was investigated by measuring electrical conductivity, ionic transference number, and Seebeck coefficient. The β-Bi2 O3 doped with 1 to 10 mol% Sb2 O3 was stable up to 600°C and showed an oxygen ionic and electronic mixed conduction, where the electron conduction was predominant at low oxygen pressures. The oxygen-ion conductivity showed a maximum at 4 mol% Sb2 O3 , whereas the activation energy for the ionic conduction remained unchanged for 4 to 10 mol% Sb2 O3 -doped specimens. These results were interpreted in terms of the oxygen vacancy concentration and the distortion of the tetragonal structure. The electron conductivity and its oxygen pressure dependence decreased with increasing Sb2 O3 content. The fact that Sb5+ is partially reduced by excess electrons in heavily doped β specimens at low oxygen pressures is explained. 相似文献
2.
Chemically induced grain-boundary migration and its effects on the interface and dielectric properties of semiconducting SrTiO3 have been investigated. Strontium titanate specimens that had been doped with 0.2 mol% of Nb2 O5 were sintered in 5H2 /95N2 . The sintered specimens were diffusion annealed at 1400°C in 5H2 /95N2 with BaTiO3 or 0.5BaTiO3 -0.5CaTiO3 (mole fraction) packing powder. The grain boundaries of the annealed specimens were oxidized in air. In the case of BaTiO3 packing, grain-boundary migration occurred with the diffusion of BaTiO3 along the grain boundary. The effective dielectric constant of the specimen decreased gradually as the temperature increased but showed two peaks, possibly because of barium enrichment at the grain boundary and an oxidized Sr(Ba)TiO3 layer. In the case of 0.5BaTiO3 -0.5CaTiO3 packing, although barium and calcium were present at the grain boundary of the specimen, no boundary migration occurred, as in a previous investigation. With the diffusion of barium and calcium, the resistivity of the specimen increased and the variation of the effective dielectric constant with temperature was much reduced, in comparison to those without solute diffusion. These enhanced properties were attributed to the solute enrichment and the formation of a thin diffusional Sr(Ba,Ca)TiO3 layer at the grain boundary. 相似文献
3.
Bing Zhang Qi Chen Li Song Huiping Li Fengzhen Hou 《Journal of the American Ceramic Society》2008,91(6):2036-2038
The influence of 0–16 mol% Sb2 O3 substitution for P2 O5 on the properties of ZnO–P2 O5 glasses has been investigated. It was shown that Sb2 O3 could participate in the glass network and thermal stability of the glasses decreased with increasing Sb2 O3 content. Glass transition temperature T g , softening temperature T s , and water durability all decreased firstly (up to 6 mol% Sb2 O3 added) and then increased. Substitution of 12 mol% Sb2 O3 led to a 16°C decrease in T g and 30°C decrease in T s , and weight loss of the glass was only 0.42 mg/cm2 , which is ∼11 times lower than that of the glass without Sb2 O3 after immersion in deionized water at 90°C for 1 day. The glass containing 12 mol% Sb2 O3 might be a substitute for Pb-based glasses in some applications. 相似文献
4.
Nina Daneu Aleksander Renik Slavko Bernik 《Journal of the American Ceramic Society》2003,86(8):1379-1384
Microstructure development in Sb2 O3 -doped ZnO was studied to evaluate the influence of inversion boundaries (IBs) on ZnO grain growth. In general, the addition of Sb2 O3 is believed to inhibit the ZnO grain growth via the formation of spinels and IBs, but we have shown that even the conditions of exaggerated grain growth can be created in this system. We designed an experiment for diffusional doping of ZnO under slightly increased partial pressure of Sb2 O3 . In the high-concentration regime we observed no spinels, and yet the ZnO grains were small and inhibited in growth, while in the low-concentration regime we found huge grains, several times larger than normal ZnO grains, showing an obvious exaggerated growth. By controlling the number of nuclei with IBs we can design coarse-grained microstructures even with Sb2 O3 doping, which has far-reaching implications in the production of low-voltage varistor devices. 相似文献
5.
E. F. RIEBLING 《Journal of the American Ceramic Society》1973,56(6):303-309
Binary Sb2 O3 -GeO2 glasses containing 45 mol% Sb2 O3 and ternary Sb2 O3 -B2 O3 -GeO2 glasses containing 50 mol% GeO2 were prepared. Their densities (volumes), refractive indices, and infrared spectra were determined, and their colors and high-temperature viscosities were estimated visually. Small amounts of Sb2 O3 (∼10 mol%) appear to perturb neither the Ge-O-Ge network nor those B-O-Ge networks with small B/Ge ratios (∼0.2). The B-O-Ge networks with larger B/Ge ratios (∼1.0) depolymerize in the presence of even less Sb2 O3 . Amounts of Sb2 O3 >10 mol% appear to depolymerize the Ge-O-Ge and Ge-O-B networks progressively, possibly with the formation of chains. A structurally sensitive ir isofrequency contour technique developed for ternary glass systems was applied successfully to these Sb2 O3 -B2 O3 -GeO2 glasses. These contours can thus readily detect significant network depolymerization in the absence of the usual network modifiers. 相似文献
6.
M. Drofenik A. Popovi L. Irmannik D. Kolar V. Kraevec 《Journal of the American Ceramic Society》1982,65(12):203-C
The release of oxygen during the sintering of Sb2 O3 -doped BaTiO3 ceramics containing excess TiO2 was measured using a mass spectrometer. The amount of oxygen released is proportional to the dopant concentration in the product phase. The evolution of oxygen during sintering was attributed to dissolution of the oxidized form of doped BaTiO3 in the reacting mixture and simultaneous re-crystallization of the- reduced form. 相似文献
7.
The defect structure and dielectric properties of BaTiO3 with 1 to 10 mol% Nd2 O3 additions were studied. The results indicated that neodymium occupies the barium site and charge compensation takes place by creation of titanium vacancies. The dependence of inverse electric susceptibility, spontaneous polarization, and specific heat on temperature for samples containing more than 2 mol% of Nd2 O3 were characteristic of a diffuse transformation resulting from a disordering of defects. The addition of Nd2O3 leads to a very drastic sfiift in the Curie temperature ( Tc ) of BaTiO3 ; 3 mel% Nd2 O3 addition moves Tc below room temperature. 相似文献
8.
Some effects of CaO, Na2 O, Sb2 O3 , and ZrO2 additions on Li0.3 Zn0.4 Fe2.3 O4 ferrite were studied to improve its density and other material properties. The densification behavior of the ferrite depended on the amount and type of additive. A relative density of ∼98.5% was achieved with the addition of CaO. The grain size decreased with the addition of Na2 O, CaO, and Sb2 O3 . The permeability and electrical resistivity increased with additives. CaO remarkably increased resistvity, whereas, ZrO2 increased permeability. Na2 O and Sb2 O3 increased the Curie temperature, whereas CaO and ZrO2 decreased it. These effects were attributed to mainly additive segregation on the grain boundaries, which suppressed grain-size development during the sintering of lithium zinc ferrite. 相似文献
9.
Yaping Zhang Yunxia Yang Yuwen Ou Wei Hua Jiahua Zheng Guorong Chen 《Journal of the American Ceramic Society》2009,92(8):1881-1883
Glasses with compositions 50Bi2 O3 – x Sb2 O3 –10B2 O3 –(40– x ) SiO2 ( x =0, 1, 3, 5, 8, 10) have been prepared by conventional melt quench technique. Substitution of Sb2 O3 for SiO2 exerted an obvious effect on properties of glasses, especially, increased glass transition temperature ( T g ) and crystalline temperature ( T c ) greatly. Results of infrared transmission spectra attributed the effect to the formation of new bridging bonds of Sb–O–B and Sb–O–Si in glass network. 相似文献
10.
Jung-Hae Choi Nong-Moon Hwang Doh-Yeon Kim 《Journal of the American Ceramic Society》2001,84(6):1398-1400
Pore–boundary separation in ZnO and 99.95ZnO·0.05Bi2 O3 (in mol%) specimens during sintering at 1200°C was investigated. In pure ZnO specimens, pores were attached to the grain boundaries and disappeared during the final stage of sintering. In the Bi2 O3 -doped specimens, on the other hand, many pores were separated from the boundaries and trapped inside the grains. Observation using transmission electron microscopy showed that a thin layer of Bi2 O3 -rich phase existed at the boundaries in the Bi2 O3 -doped specimens. The pore separation in 99.95ZnO·0.05Bi2 O3 specimens was explained in terms of the dihedral angle change and the high mobility of a liquid film boundary. 相似文献
11.
The dielectric properties, including the DC breakdown strength, of 1 mol% Nb5+ -doped BaTiO3 ceramics with different quantities of excess TiO2 have been investigated. The breakdown strength was found to decrease with increasing TiO2 content, but could not be readily explained by relative density and grain size effects. The decrease in the breakdown strength from a stoichiometric BaTiO3 composition to samples with excess TiO2 is believed to be due to the field enhancement effect (up to a factor of 1.40) at the BaTiO3 matrix because of the presence of a Ba6 Ti17 O40 second phase. The thermal expansion coefficient mismatch between the BaTiO3 matrix phase and the Ba6 Ti17 O40 phase may also result in a low breakdown strength. The dielectric properties of the pure Ba6 Ti17 O40 phase were also investigated and are reported herein. 相似文献
12.
The monolithic glass-forming region of the low phonon and low softening point antimony glasses containing high Sb2 O3 (40–75 mol%) in the novel quaternary K2 O–B2 O3 –Sb2 O3 –ZnO system has been found with the help of X-ray diffraction (XRD) analysis. The structure of a series of glasses with the general composition of (mol%) 15K2 O–15B2 O3 –(70− x )Sb2 O3 – x ZnO (where x =5–25) has been evaluated by infrared reflection spectral (FT-IRRS) analyses. All the glasses are found to possess a low phonon energy of around 600 cm−1 , as revealed by FT-IRRS. Their softening point ( T s ), glass transition temperature ( T g ), and coefficient of thermal expansion (CTE) have been found to vary in the ranges of 351°–379°C, 252°–273°C, and 195–218 × 10−7 K−1 , respectively. These properties are found to be controlled by their fundamental property, like the covalent character of the glasses, which is found to increase with an increase in Sb2 O3 content. In addition, the devitrified glasses have been characterized by XRD and field emission scanning electron microscopy, which manifests the presence of nanozinc antimony oxide crystals with sizes of 21–43 nm. The exhibited properties have revealed that they are a new class of versatile materials. 相似文献
13.
E. F. RIEBLING 《Journal of the American Ceramic Society》1974,57(9):373-377
Ternary Na2 O.Sb2 O3 .GeO2 glasses (with various [Na]/[Na + Sb] ratios) that contained ≥65 mol% GeO2 were prepared. Their densities (volumes), refractive indices, and infrared spectra were determined and their colors noted. The ternary glasses with ≥88 mol% GeO2 exhibit nearly additive volumes, refractivities, and frequencies for the main Ge-O vibration. Ternary glasses with lesser amounts of GeO2 exhibit a variety of behaviors, depending on the [Na]/[Na + Sb] ratio. Small amounts of Sb2 O3 cause significant volume and refraction deviations, as well as changes in νGe-O , that can be associated with gradual elimination of GeO6 octahedra. All the information supports a model for the glasses with 65 to 88 mol% GeO2 that involves a degree of depolymerization that is greater when Na2 O and Sb2 O3 are present together than when either is present alone. 相似文献
14.
Girish Madhav Kale Srinivasan Srikanth 《Journal of the American Ceramic Society》1999,82(8):2161-2165
Activity of Na2 O in the pyrochlore phase of the system Sb2 O4 -NaSbO3 has been measured as a function of temperature in the range 1073–1412 K by electromotive force (emf) measurements of the following solid-state electrochemical cells:
The solid electrolyte used in the above electrochemical cells is Na-ß-Al2 O3 , which is an excellent sodium-ion conductor in the temperature range of the measurements. From the measured reversible emf, the activity of Na2 O in the Sb2 O4 -NaSbO3 system has been calculated. The temperature dependence of the logarithm of the activity of Na2 O in various two-phase regions of the Sb2 O4 -NaSbO3 system can be represented as
No thermodynamic data have been reported earlier in the literature for the system Sb2 O4 -NaSbO3 , and the present data constitute the first thermodynamic information. 相似文献
The solid electrolyte used in the above electrochemical cells is Na-ß-Al
No thermodynamic data have been reported earlier in the literature for the system Sb
15.
Pomin Su Anil V. Virkar Camden R. Hubbard O. Burl Cavin Wallace D. Porter 《Journal of the American Ceramic Society》1993,76(10):2513-2520
Gd2 O3 -doped Bi2 O3 polycrystalline ceramics containing between 2 and 7 mol% Gd2 O3 were fabricated by pressureless sintering powder compacts. The as-sintered samples were tetragonal at room temperature. Hightemperature X-ray diffraction (XRD) traces showed that the samples were cubic at elevated temperatures and transformed into the tetragonal polymorph during cooling. On the basis of conductivity measurements as a function of temperature and differential scanning calorimetry (DSC), the cubic → tetragonal as well as tetragonal → cubic → teansition temperatures were determined as a function of Gd2 O3 concentration. The cubic → tetragonal transformation appears to be a displacive transformation. It was observed that additions of ZrO2 as a dopant, which is known to suppress cation interdiffusion in rare-earth oxide–Bi2 O3 systems, did not suppress the transition, consistent with it being a displacive transition. Annealing of samples at temperatures 660°C for several hundred hours led to decomposition into a mixture of monoclinic and rhombohedral phases. This shows that the tetragonal polymorph is a metastable phase. 相似文献
16.
Polycrystalline BaTiO3 prepared from alkoxy-derived high-purity submicron powders was studied. Highly dense bodies with uniform grain size were obtained typically by uniaxial cold-pressing at 3000 psi and isostatic pressing at 30,000 psi followed by sintering at 1300° to 1350°C in air for 0.5 to 1 h. Using the same consolidation parameters and intimate mixing of residual concentrations of highly active fine-particulate rare-earth oxides to act as grain-growth inhibitors, nearly theoretically dense bodies with a uniform microstructure and 1 to 1.5 μm grain size were obtained. Typical microstructures with well-defined 90° and 180° domain patterns characteristic of BaTiO3 : were observed. Also, an example of a checkerboard pattern resulting from a 〈111〉 ingrown twin plane in the structure which is independent of the Curie temperature was found. Electrical measurements on the undoped material indicated room-temperature dielectric constant and tan δ values of 5000±500 and 4×10−3 , respectively. Very high k values and dissipation factors were observed with the La2 O3 - and Nd2 O3 -doped samples. 相似文献
17.
The effects of the oxide additives MnO2 , Co3 O4 , and Sb2 O3 , commonly incorporated in commercial Bi2 O3 -doped ZnO varistors, on the current–voltage characteristics and microstructure of 0.25 mol% V2 O5 -doped ZnO varistors have been studied. MnO2 is the most significant additive in terms of its effects on varistor performance. Varistor performance can also be improved by increasing the V2 O5 content to 0.5 mol% in a ZnO ceramic containing 1 mol% MnO2 . Further increases in the V2 O5 content of 1 mol% MnO2 -doped material cause a deterioration in varistor behavior. The microstructure of the samples consists mainly of ZnO grains with zinc vanadates as the minority secondary phases. Additional spinel phase is formed when Sb2 O3 is incorporated. 相似文献
18.
J. LLorca José Y. Pastor Pedro Poza José I. Peña Isabel de Francisco Angel Larrea Victor M. Orera 《Journal of the American Ceramic Society》2004,87(4):633-639
The effect of Y2 O3 content on the flexure strength of melt-grown Al2 O3 –ZrO2 eutectics was studied in a temperature range of 25°–1427°C. The processing conditions were carefully controlled to obtain a constant microstructure independent of Y2 O3 content. The rod microstructure was made up of alternating bands of fine and coarse dispersions of irregular ZrO2 platelets oriented along the growth axis and embedded in the continuous Al2 O3 matrix. The highest flexure strength at ambient temperature was found in the material with 3 mol% Y2 O3 in relation to ZrO2 (Y2 O3 ). Higher Y2 O3 content did not substantially modify the mechanical response; however, materials with 0.5 mol% presented a significant degradation in the flexure strength because of the presence of large defects. They were nucleated at the Al2 O3 –ZrO2 interface during the martensitic transformation of ZrO2 on cooling and propagated into the Al2 O3 matrix driven by the tensile residual stresses generated by the transformation. The material with 3 mol% Y2 O3 retained 80% of the flexure strength at 1427°C, whereas the mechanical properties of the eutectic with 0.5 mol% Y2 O3 dropped rapidly with temperature as a result of extensive microcracking. 相似文献
19.
Scanning electron microscopy and electron probe micro-analysis were used to investigate the microstructure of both slow-cooled and quenched polycrystalline BaTiO3 specimens with a small excess of TiO2 (Ba/Ti=0.995 to 0.999) or of BaO (Ba/Ti=1.002 and 1.005). The electron micrographs of polished and etched TiO2 -excess BaTiOs samples, and of fracture surfaces of quenched samples, showed a second phase in the grain boundaries and triple-point regions, whereas no second phase was observed in samples having Ba/Ti=1.000. Microprobe analysis of the second phase gave compositions near that of the reported adjacent phase of higher TiO2 content, Ba6 Ti17 O40 . The results indicate that the solubility of TiO2 in BaTiO3 is <0.1 mol%. 相似文献
20.
Mullite transformation kinetics of sol-gel-derived diphasic mullite gels doped with P2 O5 , TiO2 , and B2 O3 were studied using quantitative X-ray diffraction and differential thermal analysis (DTA). The mullite transformation temperature initially increased with P2 O5 doping because of phase separation and formation of α-alumina and cristobalite. In TiO2 -doped samples, the mullite transformation temperature decreased with TiO2 doping, and the transformation rate increased with decreasing TiO2 particle size. Kinetic studies showed that titania reduced the activation energy for both nucleation and growth relative to pure diphasic mullite gels by lowering the glass viscosity and/or enhancing the solid-state mass transport through lattice defects. B2 O3 doping decreased the mullite transformation temperature and lowered the activation energy for both nucleation and growth but especially affected the mullite nucleation process, as indicated by the much smaller grain size. 相似文献