More conventionally deposited coatings of Er2O3 or Y2O3 were developed such as arc source plasma deposition,25 electron beam-physical vapor deposition (EB-PVD),2 and radiofrequency (RF) sputtering.26 Because of the variation in the quality of the coating and the test conditions, reported stability in liquid lithium was different in different tests. Er2O3 produced by EB-PVD was heavily damaged in Li already at 500 °C,27 and Er2O3 and Y2O3 coatings produced by RF sputtering were also exfoliated at 500 ° C.28 How­ever, Er2O3 fabricated by arc source plasma deposition showed promising results, as shown in Figure 8. Depo­sition on a higher temperature substrate produced a highly crystalline Er2O3 coating, which was shown to be stable in Li for 1000 h at 700 “C.1 The stability in Li is known to be enhanced by improving the purity and crystallinity of the coating. An oxide layer at the coating/substrate interface may cause extensive exfoli­ation because Li introduced through cracks would preferentially attack the oxidized interface.

4.21.3.3.3 Other coating technologies

The efforts in using the physical coating processes explained so far are essential for establishing the
coating concepts. However, further efforts are also necessary to enhance the engineering feasibility of coating on large and complex surfaces. For this purpose, the sol-gel method (in other words, metal-organic deposition, MOD) and metal-organic chemical vapor deposition (MOCVD) have been explored.

Er2O3 coating was formed on stainless steel by the sol-gel method. Crystallinity of the coating depended on annealing atmosphere and tempera — ture.29 MOCVD was applied to coating Er2O3 on V-alloys and other materials. Successful coating on the inner surface of a tube was demonstrated.3