The free energy of formation of GeO2(hex) by e.m.f. measurements

doi:10.1016/0022-5088(79)90050-X

Journal of the Less Common Metals

Volume 68, Issue 2, December 1979, Pages 143-152

https://doi.org/10.1016/0022-5088(79)90050-X Get rights and content

Abstract

The values of the standard free energy of formation Δ_fG⁰_m of the stable tetragonal form of GeO₂ as well as of the metastable hexagonal modification were obtained from e.m.f. measurements on the following types of cells^∗. Pt, C, Ge, GeO₂(tet)/15 wt.% Y₂O₃ZrO₂/inert gas (P_o₂≈ 10⁻⁴atm), Pt and Pt, C, Ge, GeO₂(hex)/15 wt.% Y₂O₃ZrO₂/inert gas (P_o₂ ≈ 10⁻⁴atm), Pt The e.m.f. data yielded the following least-squares expressions. Δ_F⁰_m (GeO₂, hex) ± 1.2 kJ⁻¹ = −549.86 + 0.16837 T (810−1180K) Δ⁰_m (GeO₂, tet) ± 1.15 kJ⁻¹ = − 571.39 + 0.18657 T (800 −1150 K) Combining the data for GeO₂(hex) with calorimetric data, a value of − 559.7 ± 0.9 kJ was obtained for Δ_fH⁰_m(GeO₂, hex, 298 K) from a third law plot. The transformation from GeO₂(tet) to GeO₂(hex) had an enthalpy value of − 21.5 kJ at 1176 K.

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^∗: 1 atm = 0.1013 MPa.

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The free energy of formation of GeO2(hex) by e.m.f. measurements

Abstract

Acta Metall.

J. Phys. Chem. Solids

J. Nucl. Mater.

Acta Crystallogr.

Prog. Rep. 1 on CVD Research Project RP3/33(AD293811)

Z. Anorg. Allg. Chem.

The free energy of formation of GeO₂(hex) by e.m.f. measurements