The A l-N i phase diagram has been investigated in the com position range x Ni = 0.70 to 0.97. Phase boundaries were determined by using differential thermal analysis and Knudsen effusion mass spectrometry. The measurements were carried out in the temperature range between 1409 and 1730K. An A l-N i phase diagram is obtained for x Ni Si 0.70 by com bining the data from this work with selected data from the literature. This diagram deviates from that recommended by phase diagram compilations and used generally in the literature to date; it agrees reasonably well with a diagram which has been rejected in the literature. + On leave from: Fuel Chemistry D ivision,

The vaporization of the samples of the compositions Ga2O3+ LaGaO3, LaGaO3+ La4Ga2O9, and La4Ga2O9+ La2O3 was investigated using Knudsen effusion mass spectrometry in the temperature range 1494–1937 K. The partial pressures of the gaseous species O2, Ga, GaO, Ga2O, and LaO were determined over the samples investigated. The equilibrium partial pressures were used for the calculation of the thermodynamic activities of the components at 1700 K. Gibbs energies of formation of LaGaO3(s) and La4Ga2O9(s) at 1700 K from the component oxides were derived from the thermodynamic activities as −46.4 ± 4.7 and −99.2 ± 7.9 kJ·mol−1, respectively. The results were compared with the literature data obtained using other methods.

The vaporization of LaCrO3(s) and samples of the composition LaCrO3+ La2O3 was investigated in the temperature range of 1887‐2333 K by Knudsen effusion mass spectrometry using Knudsen cells made of tungsten lined completely with iridium. The species Cr(g), CrO(g), CrO2(g), and LaO(g) were identified in the vapor. Their partial pressures were determined by calibration with pure platinum solid. The thermodynamic activity of Cr2O3, acr2o3 in LaCrO3 for the Cr203‐poor phase boundary of this phase was In aCr2o3= ‐(17953/T) ‐ 0.485 (temperature T given in K) for the temperature range of the measurements with a probable overall error of ± 13%. The following values and temperature dependence of ΔG°f,T resulted for the formation of LaCrO3(s) according to the reaction 0.5Cr2O3(s) + 0.5La2O3(s) → LaCrO3(s): ΔG°f,2100= ‐78.9 ± 1.1 kj/mol, ΔH°f,298= ‐76.8 ± 5.2 kj/mol, and ΔG°r(kJ/mol) = ‐74.7 ‐ 0.00202T. Computations for the vaporization of LaCrO3 were conducted to show the volatility of this material in different atmospheres at high temperatures.

No abstract

Vaporization of the La 0.85 Sr 0.15 Ga 0.85 Mg 0.15 O 2.85 , and La 0.90 Sr 0.10 Ga 0.80 Mg 0.20 O 2.85 perovskite phases was investigated by the use of Knudsen effusion mass spectrometry in the temperature range of 1618-1886 K. The partial pressures of the gaseous species O 2 , Mg, Sr, SrO, Ga, GaO, Ga 2 O, and LaO were determined over the samples investigated. The equilibrium partial pressures were used for the calculation of thermodynamic activities of the components at 1800 K. The results are compared with thermodynamic data of LaGaO 3 ͑s͒ without additives. Implications of the present data for the potential use of the material in solid oxide fuel cell technology are discussed as well.The La 1Ϫx Sr x Ga 1Ϫy Mg y O 3Ϫ(xϩy)/2 perovskite phase with different Sr and Mg content has recently been proposed as a possible candidate material for the electrolyte of solid oxide fuel cells ͑SOFC͒. 1 The material shows a good oxygen ion conductivity at about 800°C 2 which is comparable to that of ZrO 2 stabilized with 8 mol % Y 2 O 3 ͑YSZ͒ at 1000°C. The latter material is commonly used as the solid electrolyte in SOFCs. Electrolytes made of La 1Ϫx Sr x Ga 1Ϫy Mg y O 3Ϫ(xϩy)/2 are useful for low SOFC operating temperatures. Low operating temperatures between 750 and 800°C allow serious technological and chemical problems to be avoided. The study of the physicochemical properties of this compound is, therefore, of great practical interest. For example, the vaporization processes in the different atmospheres at the anode and cathode sides of the SOFC have to be known under operating conditions. It has been shown that lanthanum gallate vaporizes incongruently, 3,4 which can lead to changes in the chemical composition of the electrolyte and, as a consequence, to a change of its chemical and electrochemical properties. Knowledge of the potential for the decrease of this vaporization by the use of a doped LaGaO 3 ceramic electrolyte is, therefore, of practical interest. There are no studies to date dealing with the influence of the partial substitution of alkaline earth metals for La and Ga in LaGaO 3 on the volatility of the doped material.A further problem might be the alkaline earth carbonate formation in LaGaO 3 base electrolytes if H 2 /CO anode gases are used. 5 Thermodynamic activities of the alkaline earth metal oxides SrO and MgO in La 1Ϫx Sr x Ga 1Ϫy Mg y O 3Ϫ(xϩy)/2 have to be known in order to make predictions about carbonate formation. 6 This paper reports on experimental investigations of the vaporization of the La 1Ϫx Sr x Ga 1Ϫy Mg y O 3Ϫ(xϩy)/2 perovskite phase carried out by Knudsen effusion mass spectrometry. Thermodynamic activities of oxide components in La 1Ϫx Sr x Ga 1Ϫy Mg y O 3Ϫ(xϩy)/2 are determined. The results are used to predict the vaporization of La 1Ϫx Sr x Ga 1Ϫy Mg y O 3Ϫ(xϩy)/2 under SOFC operating conditions at the anode and cathode sides. Implications of the data for the potential use of La 1Ϫx Sr x Ga 1Ϫy Mg y O 3Ϫ(xϩy)/2 in SOFC technology are discussed. ExperimentalTwo samples of the compo...