Thermochemical properties of gaseous ZrO and ZrO2

Abstract

The dissociation energy of gaseous ZrO, D₀° (ZrO), and the heat of atomization of gaseous ZrO₂ have been measured using a high temperature mass spectrometer. A number of equilibria were studied and the following results were derived: Δ_fH (ZrO,g,298.15 K) =83±12 kJ/mol, D₀° (ZrO) =761±15 kJ/mol) (or 7.89±0.15 eV), Δ_fH (ZrO₂,g,298.15K) =−298±30 kJ/mol, and D₀° (ZrO₂) =1386±30 kJ/mol (or 14.4±0.3 eV). The ionization potentials of ZrO and ZrO₂ were derived from the measured appearance potentials. In the case of ZrO it was necessary to make corrections for the thermal populations of low‐lying electronic states. The derived values are I.P.(ZrO) =6.0±0.2 eV, I.P.(ZrO₂) =9.4±0.2 eV. These measurements are discussed in relation to other studies. Uncertainties in the derived thermochemical quantities owing to uncertainties in the spectral data are discussed. The chemical bonds in ZrO and ZrO₂ are briefly discussed.