Patent ID: 7740960

Claim:
A multilayer article comprising: a substrate; a bond coat in contact with said substrate, said bond coat selected from the group consisting of, mullite doped with gadolinium oxide, mullite doped with yttrium oxide, mullite doped with ytterbium oxide, mullite doped with zirconium oxide and combinations thereof; and an interlayer comprised of a plurality of sublayers external to said bond coat, said sublayers comprised of chemically distinct layers wherein the thermodynamic activity of silicon within each sublayer is not equal to the thermodynamic activity of silicon in an adjacent sublayer, said plurality of sublayers selected from the group consisting of mullite doped with silicon, mullite doped with hafnium oxide, mullite doped with gadolinium oxide, mullite doped with yttrium oxide, mullite doped with ytterbium oxide, mullite doped with zirconium oxide, mullite doped with rare earth silicates and combinations thereof.