Advanced high temperature environmental barrier coating for SiC/SiC ceramic matrix composites

An environmental barrier coating system disposed on a substrate, the coating system comprising:

• a bond coat layer disposed on the substrate, the bond coat layer comprising a rare earth (RE) silicon component and a silicate oxide component, wherein:
• the rare earth (RE) silicon component is selected from:
• a RE silicon alloy,
• a RE silicide,
• a RE doped refractory transition metal silicide,
• a RE and aluminum doped palladium, iridium, or platinum silicide,
• a RE tantalum-, titanium-, chromium-, molybdenum-, niobium-, aluminum-, silicon, carbon, boron, nitride compounds with silicon,
• one of Tix(AlCrTa)ySi—CN, Tix(AlCrTa)ySi—BN, Ti2CrTa(Si)—N, ZrTaSi—N, HfTaSiCN, and Ta2AlSi—CN, and
• a combination of two or more thereof,
• the silicate oxide component is doped or alloyed with ZrO2 or HfO2, wherein the silicate oxide component is selected from a RE mono-silicate, a RE di-silicate, or a combination thereof;
• a first environmental barrier coating (EBC) disposed on the bond coat layer, wherein the first EBC comprises a rare earth aluminosilicate compound or composite comprising a rare earth silicate composition and an alumina dopant;
• and
• a second EBC disposed on the first EBC, wherein the second EBC possesses a graded columnar structure comprising a HfO2 or ZrO2-based ceramic alloy doped with SiO2 and a RE oxide, wherein a concentration of the SiO2 dopant decreases with distance from the substrate, wherein a concentration of the RE oxide dopant increases with distance from the substrate.