Defect Structure and Transport Properties of Manganese Oxides: (I) The Nonstoichiometry of Manganosite (Mn_1‐ΔO)

Abstract

The deviation from stoichiometry Δ in manganosite (Mn1‐ΔO) has been studied thermogravimetrically as a function of oxygen activity between 900 and 1400°C. Two formal fits of the deviation from stoichiometry as a function of oxygen activity and temperature are reported. From the experimental data, it is concluded that cation vacancies and holes are the predominant defect species over most or all of the manganosite stability range at high temperatures. The electrical conduction and cation diffusion in manganosite are analyzed briefly with regard to the defect structure of this oxide.

Assessment of the Mn-O system

“…7a-c). [20,26,33,36,40,42,44,45] 2.1.3 ␣-, ␤-Hausmannite (Mn 3 O 4 ), Pyrolusite (MnO 2 ), and Bixbyite (Mn 2 O 3 ). The question of the homogeneity range of ␣-and ␤-hausmannite has been investigated by a number of authors, some of whom declare haus- [26,29,[46][47][48] while others find differing degrees of nonstoichiometry.…”

“…[35,37] There are quite a number of investigations on the composition of Mn 1−x O in equilibrium with Mn 3 O 4 [20,26,27,35,[38][39][40][41][42][43] ( Fig. 6) and on the composition of Mn 1−x O as a function of temperature and oxygen partial pressure (Fig.…”

“…The experimental data used for the optimization were measurements of the oxygen potential of Mn 1−x O as a function of x and T by Keller and Dieckmann, [42] Branski and Tallan, [33] and Hed and Tannhauser [26] (Fig. 7a-c) and the composition of Mn 1−x O in equilibrium with Mn 3 O 4 determined by Fender and Riley, [40] Hed and Tannhauser, [26] Keller and Dieckmann, [42] Schmahl and Hennings, [27] and O'Neill and Pownceby [43] (Fig. 6).…”

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

“…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). In those studies the oxygen activity in the environment of a sample was changed stepwise, and the resulting weight change was measured.…”

Thermodynamic vaporization studies of the manganese oxide–yttria stabilized zirconia (YSZ) solid solution

“…This non-stoichiometry of the MnO(s) phase is reported in Refs. 29,30 The thermodynamic data obtained in the present study for the vaporization of pure MnO(s) are compared with literature values: The enthalpy change of the reactions Eqs. (2) and (3) was computed according to the second and third law methods.…”