Measurement of Gibbs energies of formation of CoF2 and MnF2 using a new composite dispersed solid electrolyte
Tóm tắt
Gibbs energies of formation of CoF2 and MnF2 have been measured in the temperature range from 700 to 1100 K using Al2O3-dispersed CaF2 solid electrolyte and Ni+NiF2 as the reference electrode. The dispersed solid electrolyte has higher conductivity than pure CaF2 thus permitting accurate measurements at lower temperatures. However, to prevent reaction between Al2O3 in the solid electrolyte and NiF2 (or CoF2) at the electrode, the dispersed solid electrolyte was coated with pure CaF2, thus creating a composite structure. The free energies of formation of CoF2 and MnF2 are (± 1700) J mol−1; {fx37-1} The third law analysis gives the enthalpy of formation of solid CoF2 as ΔH° (298·15 K) = −672·69 (± 0·1) kJ mol−1, which compares with a value of −671·5 (± 4) kJ mol−1 given in Janaf tables. For solid MnF2, ΔH°(298·15 K) = − 854·97 (± 0·13) kJ mol−1, which is significantly different from a value of −803·3 kJ mol−1 given in the compilation by Barinet al.
Tài liệu tham khảo
Barin I, Knacke O and Kubaschewski O 1977Thermochemical properties of inorganic substances (Berlin: Springer-Verlag) p. 395
Binford J S Jr, Strohmenger J M and Hebert T H 1967J. Phys. Chem. 71 2404
Brewer L, Bromley L A, Gilles P W and Lofgren N L 1950The chemistry and metallurgy of miscellaneous materials (ed.) L L Quill (New York: McGraw-Hill) p. 76
Catalano E and Stout J W 1955J. Chem. Phys. 23 1803
Chattopadhyay G, Karkhanavala M D and Chandrasekhariah M S 1975J. Electrochem. Soc. 122 325
Egan J J 1985High Temp. Sci. 19 111
Ehlert T C and Hsia M 1972/73J. Fluorine Chem. 2 22
Jacob K T 1985Thermodynamics and kinetics of metallurgical process (eds) M Mohan Rao, K P Abraham, G N K Iyengar and R M Mallya (Calcutta: The Indian Institute of Metals) p. 91
Mah D A 1960 Bureau of Mines Report of Investigation5600 10
Mah D A and Pankratz L B 1976Bureau Mines Bull. 665 21
Rezukhina T N, Sisoeva T F, Holokhonova L I and Ippolitov E 1974J. Chem. Thermodyn. 6 883
Skelton W H and Patterson J W 1973J. Less Common Metals 31 47
Stout J W and Adams H E 1942J. Am. Chem. Soc. 64 1535
Stull D R and Prophet H 1971 JANAF Thermochemical Tables NSRDS NBS 37 U.S. Dept. of Commerce, Washington DC
Vaidehi N, Akila R, Shukla A K and Jacob K T 1986Mater. Res. Bull. 21 909
Venkatraman M and Hajra J P 1983Metall. Trans. 14A 2125