Crystallization behavior of arc-deposited ceramic barrier coatings

Al2O3 and Er2O3 were deposited by plasma-assisted physical vapor deposition using a filtered vacuum arc device. Varying the deposition conditions with respect to the substrate temperature and bias voltage, the crystallization behavior of these films was investigated by X-ray diffraction. In the case of alumina, when a bias voltage of -200 V is applied, crystallization of metastable crystal phases starts around 500 degreesC; the growth of the thermodynamically stable alpha-phase starts above 600 degreesC. This has to be compared with the thermodynamic phase transformation temperature of 1100 degreesC. For erbia, crystallization of the cubic crystal phase occurs at room temperature, when a bias voltage of -100 V is applied. Without exceeding the upper service limit, structural low activation materials can therefore be coated with stable ceramic barrier coatings. Deuterium permeation experiments performed with these types of coatings yield a permeation reduction factor of 40 in the case of alumina and 200 for erbia, respectively. (C) 2004 Elsevier B.V. All rights reserved.