Rare earth silicate environmental barrier coatings

Abstract

A vapor deposition method may include applying a first electron beam to vaporize a portion of a first target material comprising a rare earth oxide, where the first electron beam delivers a first amount of energy. The method also may include applying a second electron beam to vaporize a portion of a second target material comprising silica, where the second electron beam delivers a second amount of energy different from the first amount of energy. In some examples, the second target material is separate from the first target material. Additionally, the portion of the first target material and the portion of the second target material may be deposited substantially simultaneously over a substrate to form a layer over the substrate. A system for practicing vapor deposition methods and articles formed using vapor deposition methods are also described.

1 . A vapor deposition method comprising:
 applying a first electron beam to vaporize a portion of a first target material comprising a rare earth oxide, wherein the first electron beam delivers a first amount of energy;   applying a second electron beam to vaporize a portion of a second target material comprising silica, wherein the second electron beam delivers a second amount of energy different from the first amount of energy, and wherein the second target material is separate from the first target material;   wherein the portion of the first target material and the portion of the second target material are deposited substantially simultaneously over a substrate to form a layer over the substrate.   
     
     
         2 . The vapor deposition method of  claim 1 , wherein the layer comprises a substantially nonporous microstructure. 
     
     
         3 . The vapor deposition method of  claim 1 , wherein the layer comprises a substantially homogeneous composition. 
     
     
         4 . The vapor deposition method of  claim 1 , wherein the first amount of energy is between approximately 1.1 and approximately 2 times greater than the second amount of energy. 
     
     
         5 . (canceled) 
     
     
         6 . The vapor deposition method of  claim 1 , wherein applying the first electron beam and applying the second electron beam comprise applying an electron beam from a single energy source, the single energy source alternating between applying the first electron beam and the second electron beam. 
     
     
         7 . The vapor deposition method of  claim 1 , wherein the rare earth oxide is selected from the group consisting of an oxide of Gd, an oxide of Yb, and combinations thereof. 
     
     
         8 . The vapor deposition method of  claim 1 , wherein the layer comprises a first layer, and further comprising:
 applying a third electron beam to vaporize a portion of a third target material comprising a rare earth oxide, wherein the third electron beam delivers a third amount of energy;   applying a fourth electron beam to vaporize a portion of a fourth target material comprising silica, wherein the fourth electron beam delivers a fourth amount of energy different from the third amount of energy, and the fourth target material is separate from the third target material;   wherein the portion of the third target material and the portion of the fourth target material are deposited substantially simultaneously over the substrate to form a second layer over the substrate.   
     
     
         9 .- 12 . (canceled) 
     
     
         13 . The vapor deposition method of  claim 1 ,
 further comprising applying a third electron beam to vaporize a portion of a third target material, wherein the third electron beam delivers a third amount of energy, and   wherein the portion of the third target material is deposited, substantially simultaneously with the portion of the first target material and the second target material, over the substrate to form the layer.   
     
     
         14 . The vapor deposition method of  claim 13 , wherein the third target material comprises alumina. 
     
     
         15 . (canceled) 
     
     
         16 . The vapor deposition method of  claim 1 , wherein the layer comprises at least 50 weight percent rare earth silicate, formed by combination of at least some of the rare earth oxide and at least some of the silica. 
     
     
         17 . The vapor deposition method of  claim 16 , wherein the layer comprises a first layer formed over the substrate and a second layer formed over the first layer, the first layer comprising the rare earth disilicate, the second layer comprising the rare earth monosilicate. 
     
     
         18 . (canceled) 
     
     
         19 . A system comprising:
 a vacuum chamber;   
       a first electron beam source configured to deliver a first electron beam to vaporize a portion of a first target material comprising a rare earth oxide, wherein the first electron beam delivers a first amount of energy;
 a second electron beam source configured to deliver a second electron beam to vaporize a portion of a second target material comprising silica, wherein the second electron beam delivers a second amount of energy different from the first amount of energy; and 
 a substrate, 
 wherein the system is configured to substantially simultaneously deposit the portion of the first target material and the portion of the second target material in a layer over the substrate, and wherein the system is configured to deliver the first amount of energy so the first amount of energy is between approximately 1.1 and approximately 2 times greater than the second amount of energy. 
 
     
     
         20 . The system of  claim 19 , wherein the system is configured to substantially simultaneously deposit the portion of the first target material and the portion of the second target material in a substantially homogeneous layer. 
     
     
         21 . The system of  claim 19 , further comprising a transonic gas stream source. 
     
     
         22 . (canceled) 
     
     
         23 . The system of  claim 19 , wherein the system is configured to substantially simultaneously deposit the portion of the first target material and the portion of the second target material in a substantially nonporous layer. 
     
     
         24 . The system of  claim 19 , wherein the system is configured to substantially simultaneously deposit the portion of the first target material and the portion of the second target material in a columnar layer. 
     
     
         25 . (canceled) 
     
     
         26 . An article comprising:
 a substrate; and   an environmental barrier coating formed over the substrate, wherein the environmental barrier coating comprises a first material having a first vapor pressure and a second material having a second vapor pressure different from the first vapor pressure, wherein the first material is deposited from a first target material that comprises a rare earth oxide by applying a first electron beam to vaporize a portion of the first target material, the first electron beam delivering a first amount of energy, wherein the second material is deposited from a second target material that comprises silica by applying a second electron beam to vaporize a portion of the second target material, the second electron beam delivering a second amount of energy, wherein the first amount of energy is between approximately 1.33 and approximately 1.47 times greater than the second amount of energy.   
     
     
         27 . The article of  claim 26 , wherein the environmental barrier coating comprises a substantially nonporous microstructure. 
     
     
         28 . The article of  claim 26 , wherein the environmental barrier coating comprises a columnar microstructure. 
     
     
         29 . The article of  claim 26 , wherein the environmental barrier coating further comprises alumina, wherein the alumina is deposited from a third target material that comprises alumina by applying a third electron beam to vaporize a portion of the third target material, the third electron beam delivering a third amount of energy. 
     
     
         30 . (canceled)