Electrochemical determination of Gibbs free energy of formation of magnesium ferrite

Ling Wang1), Huizhu Zhou1), Yanruo Hong2), and Girish M Kale3) 1) School of Chemical Engineering and Biotechnology, Hebei Polytechnic University, Tangshan 063009, China 2) Materials Science and Engineering School, University of Science and Technology Beijing, Beijing 100083, China 3) School of Process, Environmental and Materials Engineering, Department of Mining and Mineral Engineering, University of Leeds, Leeds, LS2 9JT, UK

Õª Òª£ºThe standard Gibbs free energy of formation of magnesium ferrite was determined by means of two types of solid state electrochemical cells: one using MgZr4£¨PO4£©6 £¨MZP£© as the solid electrolyte and the other using CaF2 as the solid electrolyte. The first cell was operated in the range of 950 to 1100 K. The second cell was operated in the range of 1125 to 1200 K. The reversibility of the cell EMFs was confirmed by microcoulometric titration. The Gibbs energy changes of magnesium ferrite relative to component oxides were calculated based on EMF measurements and are given by following expressions, respectively: ¡÷G Iýð = -3579-15 T £¨J/mol£© and ¡÷G IýðI =6258-24.3 T £¨J/mol£©. The results obtained from two different cells are consistent with each other. The results also are in agreement with Rao¡¯s and Tretjakov¡¯s data in the measured temperature range. When the Gibbs free energies of formation of MgO and Fe2O3 were substituted in the reaction, the Gibbs free energies of formation of MgFe2O4 was obtained in two temperature ranges and the formations are shown as follows: ¡÷G Iýð Formation = -1427394+360.5 T £¨J/mol£© and ¡÷G IýðI Formation = -1417557+351.2 T £¨J/mol£©.

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