Thermal spray powder and film that contain rare-earth element, and member provided with film

1. A coating obtained by thermal spraying a thermal spray powder, wherein

the thermal spray powder contains a rare earth element and a first diluent element that is at least one element selected from the group consisting of zinc, silicon, boron, phosphorus, titanium, calcium, strontium, barium, and magnesium,

the rare earth element is contained in the thermal spray powder in an amount of 20% by mol or more and 90% by mol or less in terms of oxide,

the first diluent element is contained in the thermal spray powder in an amount of 5% by mol or more and 60% by mol or less in terms of oxide, the thermal spray powder comprises a rare earth element compound powder in which particles having a particle diameter of 10 μm or less, account for 90% by volume or more of the rare earth element compound powder, and the coating comprises rare earth element compound portions having a size of 20 μm 2 or less,

the coating includes, in a dispersed manner, weak points that are readily attacked by plasma and derived from the first diluent element, and

under etching conditions of applying high frequency power of 1,300 W and 13.56 MHz for 20 hours while supplying an etching gas that is a 95:950:10 volume ratio mixture of carbon tetrafluoride, argon, and oxygen at a flow rate of 1.055 L/minute inside a chamber of a parallel plate plasma etching apparatus maintained at a pressure of 133.3 Pa, a sintered body of a single oxide of the first diluent element has an erosion rate of no less than 5 times the erosion rate of an yttrium oxide sintered body under the same etching conditions.

2. The coating according to claim 1 , further comprising a second diluent element that is not a rare earth element or the first diluent element and is not oxygen, wherein a sintered body of a single oxide of the second diluent element has an erosion rate under the etching conditions that is no less than 1.5 times and less than 5 times the erosion rate of an yttrium oxide sintered body under the same etching conditions.

3. A member comprising the coating according to claim 1 on its surface.

4. The member according to claim 3 , wherein the thermal spray powder is produced by granulating and sintering a raw material powder containing the rare earth element and the first diluent element.

5. The coating according to claim 1 , wherein the thermal spray powder is produced by granulating and sintering a raw material powder containing the rare earth element and the first diluent element.

6. A method of forming a coating, comprising:

preparing a thermal spray powder containing a rare earth element and a first diluent element that is at least one element selected from the group consisting of zinc, silicon, boron, phosphorus, titanium, calcium, strontium, barium, and magnesium, wherein

the rare earth element is contained in the thermal spray powder in an amount of 20% by mol or more and 90% by mol or less in terms of oxide,

the first diluent element is contained in the thermal spray powder in an amount of 5% by mol or more and 60% by mol or less in terms of oxide, the thermal spray powder comprises a rare earth element compound powder in which particles having a particle diameter 10 μm or less account for 90% by volume or more of the rare earth element compound powder, and

under etching conditions of applying high frequency power of 1,300 W and 13.56 MHz for 20 hours while supplying an etching gas that is a 95:950:10 volume ratio mixture of carbon tetrafluoride, argon, and oxygen at a flow rate of 1.055 L/minute inside a chamber of a parallel plate plasma etching apparatus maintained at a pressure of 133.3 Pa, a sintered body of a single oxide of the first diluent element has an erosion rate of no less than 5 times the erosion rate of an yttrium oxide sintered body under the same etching conditions; and

thermal spraying the thermal spray powder to obtain the coating, wherein the coating comprises rare earth element compound portions having a size of 20 μm 2 or less, and the coating includes, in a dispersed manner, weak points that are readily attacked by plasma and derived from the first diluent element.

7. The method according to claim 6 , wherein the thermal spray powder is produced by granulating and sintering a raw material powder containing the rare earth element and the first diluent element.

8. A method of producing a member with a coating on its surface, comprising:

preparing a thermal spray powder containing a rare earth element and a first diluent element that is at least one element selected from the group consisting of zinc, silicon, boron, phosphorus, titanium, calcium, strontium, barium, and magnesium, wherein

the rare earth element is contained in the thermal spray powder in an amount of 20% by mol or more and 90% by mol or less in terms of oxide,

the first diluent element is contained in the thermal spray powder in an amount of 5% by mol or more and 60% by mol or less in terms of oxide, the thermal spray powder comprises a rare earth element compound powder in which particles having a particle diameter of 10 μm or less, account for 90% by volume or more of the rare earth element compound powder, and

under etching conditions of applying high frequency power of 1,300 W and 13.56 MHz for 20 hours while supplying an etching gas that is a 95:950:10 volume ratio mixture of carbon tetrafluoride, argon, and oxygen at a flow rate of 1.055 L/minute inside a chamber of a parallel plate plasma etching apparatus maintained at a pressure of 133.3 Pa, a sintered body of a single oxide of the first diluent element has an erosion rate of no less than 5 times the erosion rate of an yttrium oxide sintered body under the same etching conditions; and

thermal spraying the thermal spray powder onto a member to form a coating on a surface of the member, wherein the coating comprises rare earth element compound portions having a size of 20 μm 2 or less, and the coating includes, in a dispersed manner, weak points that are readily attacked by plasma and derived from the first diluent element.

9. The method according to claim 8 , wherein the thermal spray powder is produced by granulating and sintering a raw material powder containing the rare earth element and the first diluent element.