wherein the metal oxide is selected from the group consisting of: aluminum oxide, {HEAD ~ yttrium oxide}, {TAIL ~ zirconium oxide} and chromium oxide, and 
wherein the metal oxide is selected from the group consisting of : aluminum oxide , { HEAD ~ yttrium oxide } , { TAIL ~ zirconium oxide } and chromium oxide , and
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH