CVD of Y2O3 from YCl3-CO2-H2-Ar gas mixtures. An experimental study

Article abstract of DOI:10.1016/0925-8388(92)90622-G

The chemical vapor deposition of Y₂O₃ from YCl₃-CO₂-H₂-Ar gas mixtures is studied in a graphite hot-wall deposition chamber. YCl₂ gas flows are generated by vaporization of liquid YCl₃ in an argon stream and controlled by recording in situ the mass loss of the YCl₃ graphite crucible with a millibalance. The deposits are performed on alumina substrates and the Y₂O₃-deposition rates are assessed in situ with a microbalance. When [CO₂]_In/[YCl₃]_In >9, the deposits consist of pure Y₂O₃; otherwise YOCl is the main deposited phase. At P = 4 kPa, the deposition process is rate controlled by surface reactions for T < 1100 °C and 500 < Q_tot < 1000 seem, whereas beyond these limits mass transfers across the boundary layer become the rate-limiting phenomena. When controlled by surface reactions, the Y₂O₃ deposition process is thermally activated with E_a 616 kJ mol^-1, k_o = 4.4·10¹¹ mg·min^-1·cm^-2·Pa^-5 and the apparent partial reaction orders are n₁ = 2; n₂ = 2; n_a = 1 and n₄ = 0 with respect to YCl₃, H₂, CO₂ and HCl.