A galvanic-cell study of (nickel + tungsten + oxygen) in the temperature range 1034 K to 1317 K

✍ Scribed by R.E. Aune; S. Sridhar; Du Sichen

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 354 KB
• Volume: 26
• Category: Article
• ISSN: 0021-9614
• DOI: 10.1006/jcht.1994.1059

✦ Synopsis

Experimental studies of the standard molar Gibbs free energy of formation of (\mathrm{NiWO}_{4}) have been carried out using a solid-state galvanic cell involving (zirconium oxide + calcium oxide) electrolyte in the temperature range (T=1034 \mathrm{~K}) to (1317 \mathrm{~K}). The galvanic cell used can be represented as

({ }^{-} \mathrm{Pt} \mid{(1-\delta) \mathrm{Ni}+\delta \mathrm{W}}\left(\right.) f.c.c.), (\mathrm{NiWO}{4}(\mathrm{~s}), \mathrm{WO}{2.72}(\mathrm{~s})(1-x) \mathrm{ZrO}_{2}+x \mathrm{CaO}|\mathrm{NiO}(\mathrm{s}), \mathrm{Ni}(\mathrm{s})| \mathrm{Pt}^{+}),

where (\delta \ll 1). The e.m.f. against temperature plot shows a break at (T \approx 1167 \mathrm{~K}), indicating a possible phase transformation occurring in the ternary mixture. These studies were complemented by (\mathrm{X})-ray-diffraction studies of some ternary mixtures equilibrated at (T=1073 \mathrm{~K}) and (1273 \mathrm{~K}). A thermodynamic assessment of (nickel + tungsten + oxygen) was carried out as part of the present work, incorporating the present results along with those available in the literature for the ternary as well as the three binaries involved. The isothermal sections at (T=1073 \mathrm{~K}) and (1273 \mathrm{~K}) are presented.