日本金属学会誌

J. Japan Inst. Metals, Vol. 60, No. 6 (1996),
pp. 589-594

Nonstoichiometry in Iron-Chromium Sulfide (Fe, Cr)1-δS at High Temperatures

Manabu Noguchi and Toshio Narita

Research Group of Interface Control Engineering, Graduate School of Engineering, Hokkaido University Kita-Ku, Kita-13, Nishi-8, Sapporo 060

Abstract:

Deviation from stoichiometric composition of ferrous-sulfide Fe1-δS and solid solution sulfides (Fe, Cr)1-δS containing Cr up to 0.3 cation fraction was measured as functions of sulfide composition ξ, sulfur pressures (1{~}10-5 Pa) and temperatures (973{~}1173 K) using a thermogravimetric technique.
Nonstoichiometry δ increased with increasing Cr content in the (Fe, Cr)1-δS and sulfur pressures, while it decreased with increasing temperature at a constant composition and sulfur pressure. Cation vacancy is a predominant lattice defect in the (Fe, Cr)1-δS sulfide, and from the Libowitz model nonstichiometry δ and sulfur activity aS could be expressed by the following relation:

\begin{equation*}
ln (\frac{aS}{δ}) = \frac{μMeS+qVMe}{RT}+\frac{4σVFeδ(2-δ)}{RT}
\end{equation*}

where μMeS is a free energy change for formation of a sulfide with stoichiometric composition as well as qVMe and σVMe are the formation and interaction energies of cation vacancies. It was observed that the values of σVMe were positive, ranging from 50 to 70 kJ/mol, independent of sulfide compositions, and the values of qVMe decreased from 56 to 17 kJ/mol with increasing sulfide composition.


(Received October 25, 1995)

Keywords:

(Fe, Cr)1-δS, Fe1-δS, cation vacancy, nonstoichiometry, Libowitz model, vacancy formation energy, vacancy interaction energy


PDF(Free)PDF (Free)     Table of ContentsTable of Contents

Please do not copy without permission.