Jacob, K. T. ; Alcock, C. B. (1975) The oxygen potential of the systems Fe+FeCr2O4+Cr2O3 and Fe+FeV2O4+V2O3 in the temperature range 750-1600°C Metallurgical and Materials Transactions B, 6 (2). pp. 215-221. ISSN 1073-5615
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Official URL: http://www.springerlink.com/content/b282n675125140...
Related URL: http://dx.doi.org/10.1007/BF02913562
Abstract
From electromotive force (emf) measurements using solid oxide galvanic cells incorporating ZrO2-CaO and ThO2-YO1.5 electrolytes, the chemical potentials of oxygen over the systems Fe + FeCr2O 4 + Cr20 3 and Fe + FeV204 + V203 were calculated. The values may be represented by the equations: 2Fe(s, I) + O2(g) + 2Cr2O3(s) → 2FeCr204 (s) ΔμO2 = - 151,400 + 34.7T (±300) cal = -633,400 + 145.5T(±1250) J (750 to 1536°C) ΔμO2 = -158,000 + 38.4T(±300) cal = -661,000 + 160.5T(±1250) J (1536 to 1700°C) 2Fe (s, I) + O2 (g) + 2V203 (s) → 2FeV204(s) ΔμO2 = - 138,000 + 29.8T(±300) cal = - 577,500 + 124.7T (±1250) J (750 to 1536°C) ΔμO2 = -144,600 + 33.45T(±300) cal = -605,100 + 140.0T(±1250) J (1536 to 1700°C). At the oxygen potentials corresponding to Fe + FeCr2O4 + Cr203 equilibria, the electronic contribution to the conductivity of ZrO2-CaO electrolyte was found to affect the measured emf. Application of a small 60 cycle A.C. voltage with an amplitude of 50 mv across the cell terminals reduced the time required to attain equilibrium at temperatures between 750 to 950°C by approximately a factor of two. The second law entropy of iron chromite obtained in this study is in good agreement with that calculated from thermal data. The entropies of formation of these spinel phases from the component oxides can be correlated to cation distribution and crystal field theory.
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ID Code: | 12840 |
Deposited On: | 11 Nov 2010 08:45 |
Last Modified: | 16 May 2016 22:06 |
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