K. Fitzner

Thermodynamic properties and cation distribution of the ZnFe2O4Fe3O4 spinel solid solutions at 900°C

Abstract The thermodynamic properties of the Fe 3 O 4 ZnFe 2 O 4 spinel solid solution were determined at 900°C by the use of the solid electrolyte galvanic cell Fe 2 O 3 + Fe 3 O 4 |O 2− |Fe 2 O 3 + Zn x Fe 3− x O 4 The activity values obtained exhibit slight negative deviation from the ideal solution model. An analysis of the free energy of mixing of the spinel solid solution provided information on the distribution of cations between the tetrahedral and octahedral sites of the spinel lattice. This is the basis for the estimation of the free energy of formation of pure zinc ferrite from oxides. Δ G 0 ZnFe 2 O 4 = −2740 − 1.6 T cal mole −1

Electrical Resistivity of Liquid Sb-Te Solutions

The specific resistivity of liquid antimony-tellurium alloys was determined hy the DC four probe method. The cell with the capillary was used to measure potential drops in the temperature range 820 1150 K for pure antimony and six alloy compositions up to X Te = 0.6. Using experimental results obtained in the present study the resistivity change with the alloy composition at constant temperature was derived. It was demonstrated that depending on local ordering in the liquid state there is a interdependence between oxygen activity coefficient, diffusivity, and the alloy conductivity measured in Sb-Te binary system.

Gibbs free energy of formation of solid phase CUEu2O4 and CuEuO2

Abstract Employing electrochemical cells with the solid electrolyte Cu 2 O,CuEu 2 O 4 ,CuEuO 2 ¦O 2− ¦air ( p o 2 = 0.21 atm) CuEu 2 O 4 , CuEuO 2 , Eu 2 O 3 ¦O 2− ¦air ( p o 2 = 0.21 atm) the Gibbs free energy of formation of the solid CuEu 2 O 4 and CuEuO 2 phases was determined over the temperature range 1123–1373 K. The results obtained were used to derive the Gibbs free energy change of the reaction of formation of the CuEu 2 O 4 and CuEuO 2 phases from the respective oxides Cu 2 O + Eu 2 O 3 → 2CuEuO 2 Δ G 0 f = −6640 + 4.02 T (J) CuO + Eu 2 O 3 → CuEu 2 O 4 Δ G 0 f = 885−8.67 T (J) Finally, the results presented were applied to determine phase relationships in the Cu-Eu-O system at 1273 K.

Deposition of Boron Nitride on Graphite at 1300 K

A method for the deposition of BN onto graphite and other substrates is described. Boron trichloride (BCl3) and ammonia (NH3) diluted with Ar were used as reacting gases. The deposition process was carried out at 1300 K as well as lower temperatures in an open system at pressures of 1 atm. The consequences of the introduction of hydrogen to the system were considered. It was demonstrated that the replacement of argon with hydrogen increases the efficiency of the process as well as the theoretical rate of BN deposition. However, the acceleration of the deposition seems to be unprofitable, because the resulting supersaturation leads to the formation of an amorphous phase. The modification of the experimental conditions were proposed.

Gibbs free energy of formation of the solid phases Cu2Y2O5 and CuYO2 determined by the E.M.F. method

Abstract Employing the following electrochemical cells with solid zirconia electrolyte: Cu 2 Y 2 O 5 , CuYO 2 , Y 2 O 3 /O 2− /air Cu, CuYO 2 , Y 2 O 3 /O 2− /air as well as with CaF2 solid electrolyte air, CuO, Cu 2 Y 2 O 5 , YOF/F 1− /YOF, Y 2 O 3 , air Gibbs free energies of formation of the solid CuYO2 and Cu2Y2O5 phases were determined in the temperature range 973–1323 K. The results obtained in this study were used to derive the Gibbs free energy change of the reaction of formation of these two compounds from the respective oxides: ΔG f,ox ⊖ = 7265 ± 8.31T J mol −1 for the reaction: 1 2 Cu 2 O + 1 2 Y 2 O 3 = CuYO 2 and ΔG f,ox ⊖ = 6670 − 7.05T J mol −1 for the reaction: 2 CuO + Y 2 O 3 = Cu 2 Y 2 O 5

Oxygen potential and phase equilibria in the TeSb2O3Sb2O4 pseudoternary part of the SbTeO system at elevated temperatures

Abstract Employing the electrochemical cells with the solid oxide electrolyte Kanthal + Rc , Te (1), TeO 2 ( s )‖ O -2 air ; Pt Pt + Re , Sb 2 O 3 ( s ), Sb 2 O 4 ‖ O -2 air ; Pt Pt + Re , Sb 2 O 3 ( s ), Sb 2 O 4 ( s ); Te (1)‖ O -2 ‖ air ; Pt the equilibrium oxygen potential in the pseudobinary TeTeO 2 , Sb 2 O 3 Sb 2 O 4 and in the Sb 2 O 3 Sb 2 O 4 Te pseudoternary systems was determined in the temperature range 700–1173K. In addition, the pseudobinary sections Sb 2 O 3 Te, Sb 2 O 3 Sb 2 O 4 (1:1)Te and Sb 2 O 4 Te were examined by DTA in the temperature range 500–1300K. Using these results the evolution of the pseudoternary system with temperature can be suggested. It was found that, at 718K, a ternary eutectic with a composition close to pure Te appears in the system. At a higher temperature, 920K, another liquid phase is formed, which is characteristic of the ternary four-phase equilibrium L 2 + Sb 2 O 4 (s) + Sb 2 O 3 (3) = L 1 .

Determination of oxygen activity in gallium-antimony liquid solutions

The activity of oxygen occuring at low concentrations in liquid Ga-Sb solutions was studied by means of the galvanic cell with zirconia solid electrolyte: W,O in Ga-Sb | ZrO2 + CaO | air, Pt. The coulometric titration technique was employed. The activity coefficient of oxygen was determined over the whole composition range as a function of temperature in the interval 1 123 K – 1 223 K. From the experimental resultsWagners parameterh was deduced as:hGaSb=7 730J/g atom O. Values of oxygen activity coefficients in ternary gallium-indium-antimony alloys were predicted.ZusammenfassungEs wurde die Aktivität des in flüssigen Ga - Sb-Lösungen in niedrigen Konzentrationen anwesenden Sauerstoffe mittels einer galvanischen Zelle mit festem Elektrolyt: W,O in Ga - Sb|ZrO2 + CaO| Luft, Pt untersucht. Als Elektrolyt wurde mit Calciumoxid stabilisiertes Zirkoniumoxid benutzt. Es wurde dabei die coulometrische Titrierung angewendet. Der Aktivitätskoeffizient von Sauerstoff wurde als Funktion der Temperatur in einem Bereich von 0 bis 100 At% Sb ermittelt. Auf Grund von experimentellen Daten wurde derWagnersche Parameter zuh=7 730J/g Atom O ermittelt. Die Werte der Sauerstoff-Aktivitätskoeffizienten in ternären Gallium-Indium-Antimon-Legierungen wurden berechnet.

Interaction between oxygen and tin dissolved in liquid copper

Abstract Using the cell the effect of tin on the activity of oxygen in solution in liquid copper has been measured at 1373 and 1473 K. It was found that the activity of oxygen in liquid copper decreased with the addition of tin and the interaction parameter ϵ Sn O was determined as The results obtained are in satisfactory agreement with those predicted by a quasi-chemical model.

Diffusion of Oxygen in Liquid Tellurium and Sb[sbnd]Te Alloys

Abstract The diffusivity of oxygen in liquid tellurium and tellurium-antimony alloys was determined from potentiostatic experiments. In the temperature range 773–923 K the diffusivity of oxygen in liquid tellurium is: while the isothermal DO Te vs. alloy composition plot shows an s-shape dependence with a sudden rise in oxygen diffusivity around the alloy composition X Te = 0.3.

The influence of oxygen solubility on the electrochemically measured activities of metallic components in liquid Cu-Ag solutions

Abstract The activity of copper in the Cu-Ag liquid alloys was studied in a high temperature galvanic cell using calcia stabilized zirconia as a solid oxide electrolyte. Experiments were performed over the temperature range 1150-1300 K and in the range of Xcu from 0.2 to 0.7 mole fraction. The activities were found to exhibit positive deviation from ideal behaviour and agreed well with those reported in literature. The influence of oxygen on the electrochemically measured thermodynamic functions of metallic components was estimated at 1373 K, using previously determined solubility data