“…The application of triode sputtering (30,32,40), dc (4,5,22,33,38,(44)(45)(46)(47)(48)(49)(50)(51)(52)(53)(54)(55)(56)(57)(58)(59)(60)(61) and rf magnetron sputtering (31,(34)(35)(36)(37)(38)(39)(40)(41)(42)(43), electron-beam evaporation (20)(21)(22)(23)(24)(25)(26)(27), and arc evaporation (28,29) for the deposition of boride coatings is reported in the literature. Because of the low electrical and thermal conductivity of boron (22) and because of the high reactivity of certain rare-earth metals with oxygen (e.g., lanthanum and cerium), most PVD processes make use of the corresponding boride as the vapor source in...…”