Table 4 Chemical properties of Ge, Zr, and O and thermodynamic parameters of related oxides

Ionic radius, Å

0.53 [Ge⁴⁺]

0.79 [Zr⁴⁺]

1.40 [O²⁻]

Atomic radius, Å

1.23

1.60

0.66

Electronegativity, χ

2.01

1.33

3.44

Electronegativity difference upon bond formation, χ_M-χ_O

1.43

2.11

0

Coordination number in the M-O bond

4

7

-

Type of M-O bond

covalent polar

ionic

-

Length of M-O bond, Å

1.77

2.13

-

Standard molar enthalpy of the oxide formation

at 298.15 K, Δ_fH⁰ kJ/mol

−261.9 (GeO)

−580.0 (GeO₂)

−1100.6 (ZrO₂)

-

Standard molar Gibbs energy of the oxide formation at 298.15 K, Δ_fG⁰, kJ/mol

−237.2 (GeO)

−521.4 (GeO₂)

−1042.8 (ZrO₂)

-