A quartz structure includes a protective layer comprising yttrium oxide. The quartz structure may be fabricated by: (a) receiving a quartz structure; and (b) coating the quartz structure with a protective layer comprising yttrium oxide to form a part to be used in the plasma reactor. The part has a size and shape adapted for forming a window or injector in a plasma reactor. The protective layer does not substantially change the size or shape of the quartz structure. The part may be installed in the plasma reactor at a location where, during operation, a plasma will contact or be proximate to the part.