A method for applying a coating 1 to a surface 2 of a mullite material 3 is specified, which comprises pretreating the surface 2 of the mullite material 3 by means of a plasma-chemical process in which molecular hydrogen is excited in such a way that plasma-activated hydrogen is produced S1, and applying an aluminum oxide-containing layer 4 by means of a PVD process to the pretreated surface 2 of the mullite material 3 S2. Furthermore, a mullite material 3 with a coating and a gas turbine component with such a mullite material 3 are specified.

A method for applying a coating 1 to a surface 2 of a mullite material 3 is specified, which comprises pretreating the surface 2 of the mullite material 3 by means of a plasma-chemical process in which molecular hydrogen is excited in such a way that plasma-activated hydrogen is produced S1, and applying an aluminum oxide-containing layer 4 by means of a PVD process to the pretreated surface 2 of the mullite material 3 S2. Furthermore, a mullite material 3 with a coating and a gas turbine component with such a mullite material 3 are specified.

A method for forming a protective coating on a surface of a ceramic substrate includes combining a rare-earth oxide, alumina, and silica to form a powder, etching the surface of the ceramic substrate, applying the powder on the etched surface in an amount of from about 0.001 to about 0.1 g/cm.sup.2 to reduce capture of bubbles from off-gassing of the ceramic substrate, heating the powder for a time of from about 5 to about 60 minutes to a temperature at or above the melting point such that the powder melts and forms a molten coating on the surface that has a minimized number of bubbles, and cooling the molten coating to ambient temperature to form the protective coating disposed on and in direct contact with the surface of the ceramic substrate such that the protective coating has a thickness of less than about 1 mil.

A method for forming a protective coating on a surface of a ceramic substrate includes combining a rare-earth oxide, alumina, and silica to form a powder, etching the surface of the ceramic substrate, applying the powder on the etched surface in an amount of from about 0.001 to about 0.1 g/cm.sup.2 to reduce capture of bubbles from off-gassing of the ceramic substrate, heating the powder for a time of from about 5 to about 60 minutes to a temperature at or above the melting point such that the powder melts and forms a molten coating on the surface that has a minimized number of bubbles, and cooling the molten coating to ambient temperature to form the protective coating disposed on and in direct contact with the surface of the ceramic substrate such that the protective coating has a thickness of less than about 1 mil.

A process for treating a fused refractory product including more than 10% by mass of ZrO.sub.2, or “base product.” The process includes heating at least a portion of the surface of the product, so as to melt ZrO.sub.2 crystals in a superficial region extending to a depth of less than 2000 μm. The process includes cooling the molten superficial region obtained in the preceding step so as to obtain a protective layer.

A process for treating a fused refractory product including more than 10% by mass of ZrO.sub.2, or “base product.” The process includes heating at least a portion of the surface of the product, so as to melt ZrO.sub.2 crystals in a superficial region extending to a depth of less than 2000 μm. The process includes cooling the molten superficial region obtained in the preceding step so as to obtain a protective layer.

A bond sublayer is applied to a part and a ceramic layer is deposited on the bond sublayer by plasma spraying. The ceramic layer is then sintered.

A method for forming a component for a plasma processing chamber is provided. An internal mold is provided. An external mold is provided around the internal mold. The external mold is filled with a ceramic powder, wherein the ceramic powder surrounds the internal mold. The ceramic powder is sintered to form a solid part. The solid part is removed from the external mold.

A process of coating a substrate containing silicon with an environmental barrier coating, comprising altering a surface of the substrate and applying an environmental barrier layer to the surface of the substrate.

A process of coating a substrate containing silicon with an environmental barrier coating, comprising altering a surface of the substrate and applying an environmental barrier layer to the surface of the substrate.