A multilayered coating system consisting of a multicomponent zirconia-base
or hafnia-base oxide top layer, an interlayer comprised of a plurality of
sublayers and a bond coat layer is provided. The multilayered coating
system of the present invention, with an interlayer comprised of a
plurality of sublayers, provides a protective coating solution for
silicon-base ceramic components exposed to very high temperatures and/or
high gas flow velocity water vapor combustion environments. The plurality
of sublayers affords for a multitude of interfaces that aid in phonon
scattering within the coating system and thereby reduces its thermal
conductivity. Furthermore, the plurality of interlayer sublayers afford a
strain tolerant buffer between the top layer and substrate and thereby
accommodate the thermal expansion mismatch between the oxide top layer
(coefficient of thermal expansion (CTE) up to .about.8-10.times.10.sup.-6
m/m-C) and the silicon-base ceramic substrate
(CTE.apprxeq.4-5.times.10.sup.-6 m/m-C).