Phase relations of solid ZnO-SiO
2, ZnO-SiO
2-CaO, ZnO-SiO
2-Al
2O
3 and ZnO-SiO
2-MgO systems at 1073K have been determined by the X-ray diffraction and X-ray microanalysis studies of quenched samples. And the e.m.f. measurements using the stabilized zirconia solid electrolytes have been carried out to determine the activities of zinc oxide in solid ZnO-SiO
2 and ZnO-SiO
2-CaO systems, the activities of zinc in liquid Au-Zn alloys and the standard free energy of formation of Cu
20 and ZnO. The results are summarized as follows:(1) In ZnO-SiO
2 system, the activities of zinc oxide were represented by a single value of azno=1.0 over the range Nzno=0.67-1.0, while at Nsio=0.33-1.0 they showed also a single value but of around 0.2 at 973 and 1073 K. The standard free energy change of formation of Zn
2SiO
4 from ZnO and SiO
2 was determined as follows:
ΔG
°r/J·mol
-1 (Zn
2SiO
4)=-46590+16.79T/
K (973-1073K).
(2) In ZnO-SiO
2-CaO system, the activities of zinc oxide showed a single value of azno=1.0 in the compositions near the pure ZnO at 973-1073K. In ZnO-SiO
2-Al
2O
3 and ZnO-SiO
2-MgO systems, solid solubilities of SiO
2, Al
2O
3, MgO in ZnO phase were negligible small and it was considered that the activities of zinc oxide showed a single value of aznO=1.0 in the compositions near the pure ZnO.
(3) In liquid Au-Zn alloys, the activities of zinc showed considerable negative deviation from Raoult's law at 1023, 1073
K and agreed well with published data.
(4) The standard free energy of formation of Cu
20 and ZnO were determined as follows:ΔG
°Cu 2O/J·mol
-1=-166690+71.03T/
K±100 (871-1317
K)
ΔG
°znO/J·mol
-1=-355940+108.53T/K±190 (823-1073K).
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