Tetsu-to-Hagane
Online ISSN : 1883-2954
Print ISSN : 0021-1575
ISSN-L : 0021-1575
Standard Free Energies for Formation of Iron Oxides and Other Metal Oxides.
Study on oxygen concentration cells at high temperature-III
Kazuhiro GOTOYukio MATSUSHITA
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1964 Volume 50 Issue 8 Pages 1167-1175

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Abstract

The standard free energies for formation of several metal oxides were determined by electromotive force measurements of reversible oxygen concentration cells. Zircorria, stabilized with calcium oxide, was used as the electrolyte, which performed as a pure anion conductor due to the movement of oxygen lattice defects at high temperature above 500°C.
The measurement has been carried out extensively on many different structures of the cells, including the cells with four electrodes.
The obtained results are as follows:
(1) Fe(α)+1/2O2(G)=FeO(s)
ΔG°f=57, 610+14.13T(°C)±300Cal
(500°C-up to transformation point of α→γiron)
(2) 3Fe(α)+2O2(G)=Fe3O4(s)
ΔG°f=-236, 600+63.33T(°C)±1000Cal
(500°C-up to transformation point of α→γiron)
(3) Pb(l)+1/2O2(G)=PbO(S. or l)
ΔG°f=-45, 710+23.47T(°C)±100Cal (500°C-M.P. of PbO)
ΔG°f=-40, 840+17.82T(°C)±100Cal(M.P. of PbO-1150°C)
(4) Sn(l)+1/2O2(G)=SaO(s)
ΔG°f=-61, 000+23.72T(°C)±50Cal (500°C-1100°C)
(5) Cu(s)+1/2O2(G)=CaO(s)
ΔG°f=33, 640+23.66T(°C)±300Cal (500°C-900°C)
(6) 2Cu(s)+1/2O2(G)=Cu2O(s)
ΔG°f=-35, 360+16.98T(°C)±100Cal (500°C-M.P. of Cu)
(7) 2Ta(s)+5/2O2(G)=Ta2O6(s)
ΔG°f=-413, 800+70.66T(°C)±300Cal (800°C-1200°C)
The accuracy of the above data was discussed in comparison with the previous data. Also, the reversibility, and polarization effects of the cells were discussed.

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© The Iron and Steel Institute of Japan
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