Kinetics of deposition of zirconia-based ceramics from ZrCl4-H2-CO2-Ar gas mixtures

Article abstract of DOI:10.1016/0925-8388(92)90621-F

The kinetics of deposition of zirconia from the overall reaction: ZrCl₄(g) + 2H₂(g) + 2CO₂(g) → ZrO₂(s) + 2CO(g) + 4HCl(g) was studied from an experimental standpoint. A specially designed chemical vapor deposition reactor, equipped with a microbalance and accurate devices for controlling the experimental parameters (and especially the gas phase composition), was used to measure reliable growth rates of the ZrO₂ films over wide ranges of temperature, pressure, total flow rate and gas phase composition. The influence of the partial pressures of ZrCl₄, H₂, CO₂, Cl₂, HCl and argon was quantitatively investigated and the data used to derive kinetic laws. Finally, a tentative model of the chemical deposition process is proposed. It assumes three steps: (i) chemisorption of CO₂ on the substrate, (ii) reaction of adsorbed CO₂ with H₂ molecules resulting in H₂O adsorbed species and (iii) reaction of one ZrCl₄ molecule with two H₂O adsorbed species yielding zirconia and HCl, the third step being considered as the rate limiting step.