| abstract |
An article comprises a body and at least one protective layer on at least one surface of the body. The at least one protective layer is a thin film having a thickness of less than approximately 20 microns that comprises a ceramic selected from a group consisting of Y 3 Al 5 O 12 , Y 4 Al 2 O 9 , Er 2 O 3 , Gd 2 O 3 , Er 3 Al 5 O 12 , Gd 3 Al 5 O 12 and a ceramic compound comprising Y 4 Al 2 O 9 and a solid-solution of Y 2 O 3 —ZrO 2 . |