Journal article

Publication year: 1998

Pages: 197-218

Journal: Zeitschrift für Physikalische Chemie

Volume number: 206

ISSN: 0942-9352

DOI Link: https://doi.org/10.1524/zpch.1998.206.Part_1_2.197

Publisher: De Gruyter

Abstract: 

The electrical conductivity a of single crystalline Mn2SiO4 (tephroite) grown from the melt, was investigated by impedance spectroscopy between 1101 and 1197 degrees C as function of oxygen activity within the range similar to 10(-16) less than or equal to a(O2) less than or equal to 0.21 (air). Mn2SiO4 is n-conducting within the low and p-conducting within the high oxygen-activity regime, independent whether the sample are buffered against MnO or MnSiO3.

Based on our experimental results we propose a point-defect model the majority defects of which are vacancies in the manganese sublattice V-Mn", Mn3+-ions on Si-lattice sites Mn-Si', holes h(.) (= Mn-Mn(.)) and electrons e'.

Unlike Fe2SiO4 (fayalite), wherein according to thermogravimetric results of Nakamura and Schmalzried [1] associates (Fe-Fe. Fe-Si')(x) exist, our defect model works without postulating the analogous species {Mn-Mn. Mn-Si'}(x) to exist in tephroite. We drew this conclusion from the 1/5.5-power law which is followed by our sigma-a(O2)-plots measured on stoichiometric tephroite in the high-a(O2) regime, whereas Nakamura and Schmalzried derived an 1/5.0 power law from their measurements in the range of similar oxygen activities on likewise stoichiometric fayalite.

The equilibrium constants for formation reactions of the aforementioned defects, which emerged from our experiments were used to depict Kroger-Vink diagrams;they describe the dependence of defect concentrations on oxygen activities for both MnO resp. MnSiO3 buffered tephroite.

Harvard Citation style: Stuber, C. and Laqua, W. (1998) Point defects of tephroite.: I:: The electrical conductivity of Mn₂SiO₄, Zeitschrift für Physikalische Chemie, 206, pp. 197-218. https://doi.org/10.1524/zpch.1998.206.Part_1_2.197

APA Citation style: Stuber, C., & Laqua, W. (1998). Point defects of tephroite.: I:: The electrical conductivity of Mn₂SiO₄. Zeitschrift für Physikalische Chemie. 206, 197-218. https://doi.org/10.1524/zpch.1998.206.Part_1_2.197