Calcium-magnesium aluminosilicate (CMAS) resistant thermal and environmental barrier coatings

An apparatus, comprising:

• a substrate, wherein the substrate is made of a material selected from the group consisting of a nickel-based superalloy, a ceramic oxide, a silicon-based material, and a silicon carbide composite;
• a bond coat layer comprising silicon (Si), a HfO2—Si based coating system, a Rare Earth (RE)-Si-based bond coat, or a combination thereof disposed on the substrate;
• a coating layer disposed on the bond coat layer, wherein the coating layer comprises:
• a base oxide of hafnia, zirconia, or a combination thereof;
• and
• a plurality of rare earth dopants, wherein the rare earth dopants comprise from 5 to 20 mol % of the coating layer, wherein the plurality of rare earth dopants comprise:
• a primary stabilizer dopant comprising yttria, dysprosia, euria, or combinations thereof;
• a first cluster dopant oxide, which has a larger ionic size than the primary stabilizer dopant, comprising neodymium, samarium, europium, gadolinium, or combinations thereof;
• a second cluster dopant oxide, which has a smaller ionic size than the primary stabilizer dopant, comprising ytterbium, holmium, lutetium, or combinations thereof;
• and
• a calcium oxide dopant, which comprises from 1 mol % to 10 mol % of the coating layer;
• a first barrier layer disposed directly on the bond coat layer, wherein the first barrier layer comprises one or more of a rare earth doped mullite, a rare earth aluminum garnet, and a rare earth aluminosilicate oxygen barrier layer;
• a second barrier layer disposed directly on the first barrier layer between the first barrier layer and the coating layer, wherein the second barrier layer comprises a multi-component rare earth silicate,
• wherein the multi-component rare earth silicate has a rare earth (“RE”) composition of RE2Si2-XO7-2X, with X being between 0 and 1.95.