Environmental barrier coatings

A method for coating a gas turbine engine component, comprising:

• forming a silicon bondcoat on the gas turbine engine component, wherein the silicon bondcoat includes a sintering aid;
• forming a silicate-based layer on the silicon bondcoat with a thermal spray process;
• and
• heat treating the gas turbine engine component such that the sintering aid diffuses into the silicate-based layer to form a rare earth silicate-based hermetic portion adjacent to the silicon bondcoat and a rare earth silicate-based non-hermetic portion thereon, wherein the rare earth silicate-based hermetic layer has an elastic modulus of from 100 GPa to 180 GPa, and wherein the at least one rare earth silicate-based non-hermetic layer has an elastic modulus ranging from 50 GPa to 100 GPa.

A method for coating a gas turbine engine component, comprising:

• forming a silicon bondcoat on the gas turbine engine component;
• forming an intermediate layer on the silicon bondcoat, wherein the intermediate layer includes a sintering aid;
• forming a silicate-based layer on the intermediate layer with a thermal spray process;
• and
• heat treating the gas turbine engine component such that the sintering aid diffuses into the silicate-based layer to form a rare earth silicate-based hermetic portion closest to the silicon bondcoat and a rare earth silicate-based non-hermetic portion thereon, wherein the rare earth silicate-based hermetic layer has an elastic modulus of from 100 GPa to 180 GPa, and wherein the at least one rare earth silicate-based non-hermetic layer has an elastic modulus ranging from 50 GPa to 100 GPa.