Influence of the concentration of ZrCl4 on texture, morphology and growth rate of CVD grown α-Al2O3 coatings deposited by the AlCl3/ZrCl4/H2/CO2/H2S process

The influence of the concentration of ZrCl4 on the deposition rate, coating composition and texture of α-Al2O3 grown by Chemical Vapour Deposition by means of the AlCl3/ZrCl4/CO2/H2S/H2 process has been investigated. It was found that a very strong (300) texture was developed when ZrCl4 was added to the reaction gas mixture but also that the deposition rate increased markedly. Typically the deposition rate increased more on the edges of the inserts than on the flat surfaces. The increased deposition rate is explained in terms of a catalytic effect of ZrCl4 on a homogeneous gas reaction. No clear-cut answer to the cause of the strong (300) texture could, however, be presented but a mechanism based on a blocking of unfavourable Al2O3 surface sites by ZrCl4 is suggested as the most plausible.