We Claim:
1. An article (10) comprising:
a substrate (12) comprising a silicon-including material;
an environmental barrier coating (EBC) 16 disposed over the substrate
(12);
a bondcoat (14) disposed between the substrate (12) and the EBC (16), the bondcoat (14) comprising silicon; and
a boron source (20) disposed to provide an effective amount of boron to form an oxide (18) comprising silicon and at least 0.1 weight percent boron during exposure of the bondcoat (14) to an oxidizing environment at a temperature greater than 900 degrees Celsius.
2. The article (10) as claimed in claim 1, wherein the oxide (18) comprises at least about 0.5 wt% boron.
3. The article (10) as claimed in claim 1, wherein the oxide (18) comprises no more than about 10 wt% boron.
4. The article (10) as claimed in claim 1, wherein the oxide (18) is substantially amorphous and substantially devitrification resistant.
5. The article (10) as claimed in claim 1, wherein the oxide (18) is disposed between the bondcoat (14) and the EBC (16).
6. The article (10) as claimed in claim 1, wherein the bondcoat (14) includes the boron source (20).
7. The article (10) as claimed in claim 1, wherein the substrate (12), the EBC (16), or both of these, include the boron source (20).
8. The article (10) as claimed in claim 1, wherein the boron source (20) includes elemental boron in silicon solid solution.
9. The article (10) as claimed in claim 1, wherein the boron source (20) includes a compound including boron.

10. The article (10) as claimed in claim 1, wherein the EBC (16) includes at least one of a porous layer (430) proximate the bondcoat (14) and a hermetic layer (540).
11. The article (10) as claimed in claim 10, wherein the EBC (16) includes the boron source (20).
12. The article (10) as claimed in claim 1, wherein at least a portion of the boron source (20) is interposed between at least a portion of the bondcoat (14) and at least a portion of the EBC (16).
13. The article (10) as claimed in claim 12, wherein at least one other portion of the boron source (20) is disposed within the substrate (12), the EBC (16), the bondcoat (14), or combinations including any of the foregoing.
14. The article (10) as claimed in claim 1, further comprising a layer of oxide (18) disposed between the EBC (16) and the bondcoat (14), wherein the layer of oxide (18) comprises silicon and at least about 0.1 weight percent boron.
15. The article (10) as claimed in claim 1, wherein the silicon-including material of the substrate (12) is a ceramic matrix composite (CMC).