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1.
The electrical conductivity of polycrystalline SrTiO3 was determined for the oxygen partial pressure range of 10° to 10?22 atm and temperature range of 800 to 1050°C. The data were found to be proportional to the power of the oxygen partial pressure for the oxygen pressure range 10?15–10?22 atm, proportional to for the oxygen pressure range 10?8–10?15 atm, and proportional to for the oxygen pressure range 100–10?3 atm. These data are consistent with the presence of very small amounts of acceptor impurities in SrTiO3. 相似文献
2.
The electrical conductivity of polycrystalline strontium titanate with ( was determined for the oxygen partial pressure range of 100 to 10?22 atm and the temperature range of 850–1050°C. These data were found to be similar to that obtained for the sample with ideal cationic ratio. The observed data were proportional to the power of oxygen partial pressure for PO2 < 10?15atm, proportional to for the pressure range 10?8–10?15 atm, and proportional to for PO2 > 10?4atm. The deviation from the ideal Sr-to-Ti ratio was found to be accommodated by neutral vacancy pairs, (V″Sr V″0. The results indicate that the single-phase field of strontium titanate extends beyond 50.505 mole% TiO2 at elevated temperatures. 相似文献
3.
The electrical conductivity and departure from the stoichiometry of Nd2O3 have been measured over the temperature range of 900° to 1100°C and oxygen partial pressure of 1 to 10?16 atm. The hole conductivity of Nd2O3 is found to be proportional to , where n are 4.6, 4.9, and 5.1 at 900°, 1000°, and 1100°C, respectively. From the oxygen partial pressure dependence of the hole conductivity, it is shown that the predominant point defects in nonstoichiometric NdO1·+x are fully ionized and partially doubly ionized metal vacancies. From the thermogravimetric measurements, the departure from stoichiometry, x in NdO1·5+x, is 2.0 × 10?3 at 1000°C and 1 atm. By combining the electrical conductivity and weight change data, it is shown that the hole mobility is 6.3 × 10?4 (cm2/V·sec) at 1000°C and 1 atm. 相似文献
4.
Takamasa Ishigaki Shigeru Yamauchi Junichiro Mizusaki Kazuo Fueki Hifumi Tamura 《Journal of solid state chemistry》1984,54(1):100-107
The tracer diffusion coefficient, , of oxide ions in LaCoO3 single crystal was determined over the temperature range of 700–1000°C by a gas-solid isotopic exchange technique using 18O tracer. For the determination, two methods, the gas phase analysis and the depth profile measurement, were employed. Under an oxygen pressure of 34 Torr, the temperature dependence of in LaCoO3 was expressed by at 950°C was found to be proportional to P?0.35O2. The diffusion of oxide ions occurs through a vacancy mechanism. The activation energy for the migration of oxide ion vacancies was estimated as 18 kcal · mole?1. 相似文献
5.
The mutual solubilities of {xCH3CH2CH2CH2OH+(1-x)H2O} have been determined over the temperature range 302.95 to 397.75 K at pressures up to 2450 atm. An increase in temperature and pressure results in a contraction of the immiscibility region. The results obtained for the critical solution properties are: To(U.C.S.T.) = 397.85 K and xo = 0.110 at 1 atm; at p < 400 atm and at 800 atm < p < 2500 atm; . 相似文献
6.
The electrical conductivity of sintered specimens of nonstoichiometric CeO2?x was measured as a function of temperature (750–1500°C) and oxygen pressure (1–10?22 atm). The isothermal compositional dependence of the electrical conductivity of CeO2?x was determined by combining recently obtained thermodynamic data, x = x(PO2, T), with the conductivity data. The compositional and temperature dependence of the electrical conductivity may be represented by the expressionover the temperature range 750–1500°C and from x = 0.001 to x = 0.1.This expression was rationalized in terms of the following simple relations for (a) the electron carrier concentrationwhere nCe′Ce is the number of Ce′Ce per cm3 and a0 is the lattice parameter and (b) the electron mobility. 相似文献
7.
Junichiro Mizusaki Masafumi Yoshihiro Shigeru Yamauchi Kazuo Fueki 《Journal of solid state chemistry》1985,58(2):257-266
In order to elucidate the defect structure of the perovskite-type oxide solid solution La1?xSrxFeO3?δ (x = 0.0, 0.1, 0.25, 0.4, and 0.6), the nonstoichiometry, δ, was measured as a function of oxygen partial pressure, PO2, at temperatures up to 1200°C by means of the thermogravimetric method. Below 200°C and in an atmosphere of PO2 ≥ 0.13 atm, δ in La1?xSrxFeO3?δ was found to be close to 0. With decreasing log PO2, δ increased and asymptotically reached . The value corresponding to was about ?10 at 1000°C. With further decrease in log PO2, δ slightly increased. For LaFeO3?δ, the observed δ values were as small as <0.015. It was found that the relation between δ and log PO2 is interpreted on the basis of the defect equilibrium among Sr′La (or V?La for the case of LaFeO3?δ), V··O, Fe′Fe, and Fe·Fe. Calculations were made for the equilibrium constants Kox of the reaction and Ki for the reaction Using these constants, the defect concentrations were calculated as functions of PO2, temperature, and composition x. The present results are discussed with respect to previously reported results of conductivity measurements. 相似文献
8.
The standard enthalpy of formation of γ-UO3 has been critically assessed; the value ?(292.5 ± 0.2) kcalth mol?1 is suggested.The enthalpies of solution of β-UO3 and γ-UO3 in 3 M H2SO4 have been measured and used to derive: 相似文献
9.
Calorimetric measurements of the enthalpy of solution of cesium chromate gave ΔHsoln = (7622 ± 24) calth mol?1 for a dilution of Cs2CrO4·21128H2O. This result, along with the enthalpy of dilution gave the standard enthalpy of solution, ΔHsolno = (7512 ± 31) calth mol?1, whence the standard enthalpy of formation, ΔHf0(Cs2CrO4, c, 298.15 K), was calculated to be ?(341.78 ± 0.46) kcalth mol?1. Recomputed thermodynamic data for the formation of the other alkali metal chromates have been tabulated. From their solubilities and enthalpies of solution, the standard entropies, S0(298 K), of BaCrO4 and PbCrO4 were estimated to be (38.9 ± 0.9) and (43.7 ± 1.2) calth K?1 mol?1, respectively. There is evidence that ΔHf0(SrCrO4, c, 298.15 K) may be in error. Thermochemical, solubility, and equilibrium data, have been combined to update the thermodynamic properties of the aqueous chromate (CrO42?), bichromate (HCrO4?), and dichromate (Cr2O72?) ions. The new values at 298.15 K are as follows:
CrO42?(aq) | (13.8 ± 0.5) | ?(210.93 ± 0.45) | ?(174.8 ± 0.5) |
HCrO4?(aq) | (46.6 ± 1.8) | ?(210.0 ± 0.7) | ?(183.7 ± 0.5) |
Cr2O72?(aq) | (67.4 ± 3.9) | ?(356.5 ± 1.5) | ?(312.8 ± 1.0) |