Article including environmental barrier coating system, and method for making

An article for use in a high temperature environment, comprising:

• a substrate comprising silicon;
• a bondcoat comprising silicon, said bondcoat disposed over said substrate;
• an intermediate barrier, said barrier substantially free of mullite and comprising
• a. a first layer disposed over said bondcoat and comprising at least one of lutetium disilicate, ytterbium disilicate, yttrium disilicate, and combinations thereof, and
• b. a second layer disposed over said first layer, said second layer comprising at least one of lutetium disilicate, ytterbium disilicate, yttrium disilicate, and combinations thereof, and further comprising at least one of lutetium monosilicate, ytterbium monosilicate, yttrium monosilicate, and combinations thereof;
• and
• a topcoat disposed over said intermediate barrier, said topcoat comprising at least one of lutetium monosilicate, ytterbium monosilicate, yttrium monosilicate, and combinations thereof.

An article for use in a high temperature environment, comprising:

• a substrate comprising silicon;
• a bondcoat comprising silicon, said bondcoat disposed over said substrate;
• an intermediate barrier disposed over said bondcoat, said barrier comprising at least one layer, wherein said at least one layer is substantially free of mullite and comprises lutetium disilicate, ytterbium disilicate, yttrium disilicate, and combinations thereof, and further comprises at least one of lutetium monosilicate, ytterbium monosilicate, yttrium monosilicate, and combinations thereof;
• and
• a topcoat disposed over said barrier layer, said topcoat comprising at least one of lutetium monosilicate, ytterbium monosilicate, yttrium monosilicate, and combinations thereof.

A method for protecting an article from a high temperature environment, said method comprising:

• providing a substrate, said substrate comprising silicon;
• disposing a bondcoat comprising silicon over said substrate;
• disposing an intermediate barrier over said bondcoat, said barrier comprising at least one layer, wherein said at least one layer comprises a rare-earth silicate and is substantially free of mullite;
• and
• disposing a topcoat over said intermediate barrier, said topcoat comprising a rare-earth monosilicate.