| abstract |
An article comprises a substrate and a coating disposed over the substrate, wherein the coating comprises a monoclinic silicate phase that undergoes no solid state phase transformation reaction in the temperature range from about 1100 degrees Celsius to about 1275 degrees Celsius. Another article comprises a substrate comprising a silicon-bearing ceramic material; a bondcoat disposed over the substrate, wherein the bondcoat comprises silicon; a coating disposed over the bondcoat, wherein the coating comprises a monoclinic silicate phase, the silicate phase comprising a) yttrium and b) at least one other species selected from the group consisting of ytterbium and lutetium, wherein the material undergoes no solid state phase transformation reaction in the temperature range from about 1100 degrees Celsius to about 1275 degrees Celsius; and a topcoat disposed over the coating, wherein the topcoat comprises at least one selected from the group consisting of an aluminate, an aluminosilicate, a silicate (such as a rare earth monosilicate, for example), and zirconia. |