Thermal/environmental barrier coating for silicon-containing substrates

A barrier coating system on a silicon-containing surface of a gas turbine engine component, the barrier coating system comprising an intermediate layer and a coating composition on the intermediate layer, the intermediate layer comprising a layer formed of a material chosen from the group consisting of silicon, mullite, stoichiometric BSAS, and mixtures of mullite and stoichiometric BSAS, the coating composition consisting essentially of at least one alkaline earth-containing composition chosen from the group consisting of:

• barium strontium aluminate;
• by molar percent, about 37% to about 39% barium oxide, about 9% to about 11% strontia, about 47% to about 49% alumina, about 3% to about 5% silica, and incidental impurities;
• by molar percent, about 25% to about 26% barium oxide, about 15% to about 16% strontia, about 19% to about 21% alumina, about 39% to about 40% silica, and incidental impurities;
• by molar percent, about 20% to about 21% barium oxide, about 14% to about 16% strontia, about 42% to about 43% alumina, about 21% to about 22% silica, and incidental impurities;
• by molar percent, about 22% to about 23% barium oxide, about 14% to about 15% strontia, about 32% to about 333% alumina, about 30% to about 31% silica, and incidental impurities;
• and
• by molar percent, about 27% to about 28% barium oxide, about 9% to about 10% strontia, about 31% to about 32% alumina, about 31% to about 32% silica, and incidental impurities.