Environmental and thermal barrier coating for ceramic components

A component, comprising:

• a substrate formed of silicon nitride or silicon carbide;
• and
• a protective coating of crystalline composition on an outer surface of the substrate;
• and
• the protective coating including a mixture of tantalum oxide (Ta2O5) and an additive of at least one of Al2O3 and La2O3;
• wherein the amount of tantalum oxide is at least 50.

A method of protecting a silicon nitride (Si3N4) or silicon carbide (SiC) substrate against repeated thermal cycles at elevated temperatures, the method comprising:

• mixing an additive including an oxide, compound or precursor thereof, of at least one element chosen from the group consisting of Al, Hf, Si, Ln (rare earth including whole lanthanum series and yttrium) Mg, Mo, Ni, Nb, Sr, and Ti with a quantity of tantalum oxide (Ta2O5) powder to form a mixture, wherein the quantity of tantalum oxide is at least about 50 mol %;
• preheating the mixture;
• and
• applying the heated mixture to the substrate.

A component comprising:

• a substrate formed of silicon nitride or silicon carbide;
• and
• a protective coating for the substrate, the protective coating including tantalum oxide (Ta2O5) and La2O3 for suppressing transformation from beta Ta2O5 to alpha Ta2O5, the La2O3 being in the range of about 1-10 mol % before application of the coating;
• wherein the protective coating further includes an oxide, compound, or precursor thereof, of at least one element chosen from the group consisting of Hf, Si, Ln (rare earth including whole lanthanum series and yttrium), Mg, Mo, Ni, Sr, and Ti.

A method of applying a protective coating onto a silicon-based substrate, the method comprising:

• mixing Ta2O5 powder with AlO3 powder to create a ceramic mixture, wherein the Ta2O5 is at least about 50 mol %;
• roughening the silicon-based substrate surface;
• degreasing the silicon-based substrate surface;
• preheating the silicon-based substrate to about 1000° C.;
• applying the ceramic mixture onto the silicon-based substrate surface with an air-plasma spraying process;
• melting the ceramic mixture;
• quenching the silicon-based substrate;
• and
• solidifying the ceramic mixture into a protective coating.