Beitrag zur Metallurgie des Mangans durch thermochemische Messungen und Gleichgewichtsberechnungen

Electrochemical Investigation of the Oxygen Activity at the Manganosite‐Hausmannite Equilibrium

“…With a62 = 0.21 (oxygen activity in air) this equation leads to the following expression for the temperature dependence of the oxygen activity at the Mnl ~O/XV~na_aO4 equilibrium 4E. F log10 ao2(Mnl-aO/Mna-~O4) = log,0 0.21 R 9 T. In 10 [3] and finally, by making use of Eq. [1], one obtains log10 ao2(Mn1-~O/Mn3-~O4) = 11.5 -23,100/T [4] The results of this study are backed by the results from our independent thermogravimetric studies of the deviations from stoichiometry in manganosite, Mn~_~O (1), and in hausmannite, Mn3~O4 (2).…”

“…For the thermodynamic equilibrium between manganosite and hausmannite, some of the experimental data reported in the literature (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19) significantly scatter. The methods used for these experiments can be divided into two subgroups, namely, electrochemical and nonelectrochemical methods.…”

“…In preparation of experimental studies of the point defect chemistry in two manganese oxides, manganosite (Mnz-~O) (1) and hausmannite (Mn3_~O4) (2) we have reviewed the thermodynamic data available for the manganese-oxygen system at high temperatures. For the thermodynamic equilibrium between manganosite and hausmannite, some of the experimental data reported in the literature (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19) significantly scatter. The methods used for these experiments can be divided into two subgroups, namely, electrochemical and nonelectrochemical methods.…”

“…In general, the scatter among the electrochemically measured data [see ReL (9), (11), (12), ( 14), (15), (17), and (19)] is only relatively small, especially at high temperatures, but it is very large within the nonelectrochemically determined data sets [Ref. (3)(4)(5)(6)(7)(8), (10), (13), (16), and (18)].…”

Equilibrium Pressures of Oxygen over Mn[sub 2]O[sub 3]-Mn[sub 3]O[sub 4] at Various Temperatures

“…This was the temperature at which no Mn203 remained. Ulich and Siemonsen (6) determined heats of reaction and from these heats and other thermodynamic data calculated oxygen pressures at various temperatures. Tatievskaya et al (7) experimentally determined for Mn203, from the dissociation and oxidation approaches, the equilibrium pressures at low temperatures (up to ll00~ Also they calculated pressure-temperature equi-librium values from heats of formation and entropies.…”