Methods and Systems for the Reduction of Rare Earth Metal Oxides

Abstract

A method includes forming a powder mixture from a rare earth oxide powder and a lanthanum powder, heating the powder mixture in a crucible assembly positioned in a reduced pressure environment, wherein heating the powder mixture comprises applying heat using a heating element and heating the powder mixture reduces the rare earth oxide powder into a rare earth metal that collects on a collection region of the crucible assembly. The method also includes monitoring a pressure in the reduced pressure environment using a pressure sensor and reducing the heat applied by the heating element to the powder mixture when the pressure in the reduced pressure environment is above a threshold pressure.

What is claimed is: 
     
         1 . A method comprising:
 mixing a rare earth oxide powder and a lanthanum powder to form a powder mixture;   heating the powder mixture in a crucible assembly positioned in a reduced pressure environment, wherein:
 heating the powder mixture comprises applying heat using a heating element; and 
 heating the powder mixture reduces the rare earth oxide powder into a rare earth metal that collects on a collection region of the crucible assembly; 
   monitoring a pressure in the reduced pressure environment using a pressure sensor; and   reducing the heat applied by the heating element to the powder mixture when the pressure in the reduced pressure environment is above a threshold pressure.   
     
     
         2 . The method of  claim 1 , wherein the rare earth oxide powder comprises an ytterbium oxide powder or a gadolinium oxide powder and the rare earth metal comprises an ytterbium metal or a gadolinium metal. 
     
     
         3 . The method of  claim 1 , further comprising halting application of heat by the heating element to the powder mixture when the pressure in the reduced pressure environment is above the threshold pressure. 
     
     
         4 . The method of  claim 1 , further comprising resuming application of heat from the heating element to the powder mixture when the pressure of the reduced pressure environment is at or below the threshold pressure. 
     
     
         5 . The method of  claim 1 , wherein the powder mixture is a homogeneous mixture of rare earth oxide powder and lanthanum powder. 
     
     
         6 . The method of  claim 1 , wherein heating the powder mixture retains lanthanum in a reaction region of the crucible assembly. 
     
     
         7 . The method of  claim 1 , further comprising cooling the collection region of the crucible assembly while heating powder mixture to promote collection of the rare earth metal on the collection region. 
     
     
         8 . The method of  claim 1 , wherein the threshold pressure is in a range of from 1×10 −6  torr to 1×10 −2  torr. 
     
     
         9 . The method of  claim 1 , wherein when heating the powder mixture, the powder mixture is positioned in a reaction crucible of the crucible assembly, the crucible assembly further comprising:
 a collection crucible, wherein the collection crucible is in the collection region of the crucible assembly;   a support sleeve; and   an insulative holder, wherein the collection crucible extends into a first end of the support sleeve and the reaction crucible extends into a first end of the insulative holder; and   the method further comprises, when heating the powder mixture, cooling the collection crucible.   
     
     
         10 . The method of  claim 1 , further comprising:
 orienting a collection substrate to face the collection region of the crucible assembly holding the rare earth metal; and   sublimating the rare earth metal in an environment at a temperature in a range of from 400° C. to 3000° C. to transfer the rare earth metal from the collection region of the crucible assembly to a collection surface of the collection substrate, wherein the rare earth metal comprises an ytterbium metal.   
     
     
         11 . The method of  claim 1 , wherein the rare earth oxide powder comprises rare earth oxide particles comprising an average maximum cross-sectional dimension of 5 μm or less and a particle size distribution in which 90% or more of the rare earth oxide particles comprise a maximum cross-sectional dimension of 10 μm or less. 
     
     
         12 . A method comprising:
 forming a powder mixture from a rare earth oxide powder and a lanthanum powder; wherein the rare earth oxide powder comprises rare earth oxide particles comprising an average maximum cross-sectional dimension of 5 μm or less and a particle size distribution in which 90% or more of the rare earth oxide particles comprise a maximum cross-sectional dimension of 10 μm or less;   agitating the powder mixture to increase a distribution uniformity of the rare earth oxide powder and the lanthanum powder in the powder mixture; and   heating the powder mixture in a crucible assembly positioned in a reduced pressure environment, wherein heating the powder mixture reduces the rare earth oxide powder into a rare earth metal that collects on a collection region of the crucible assembly.   
     
     
         13 . The method of  claim 12 , wherein, subsequent to agitating the powder mixture, the powder mixture comprises a homogeneous mixture of the rare earth oxide powder and the lanthanum powder. 
     
     
         14 . The method of  claim 12 , wherein the rare earth oxide particles comprise an average maximum cross-sectional dimension in a range of 1 μm to 3 μm. 
     
     
         15 . The method of  claim 12 , wherein the lanthanum powder comprises lanthanum particles comprising an average maximum cross-sectional dimension of 90 μm or less 
     
     
         16 . The method of  claim 12 , further comprising, prior to agitating the powder mixture, positioning the powder mixture in a reaction crucible of the crucible assembly such that the powder mixture is agitated in the reaction crucible, and subsequent to agitating the powder mixture, packing the powder mixture to increase a density of the powder mixture in the reaction crucible. 
     
     
         17 . The method of  claim 12 , further comprising, prior to forming the powder mixture, milling the rare earth oxide powder to increase a sphericity the rare earth oxide particles of the rare earth oxide powder. 
     
     
         18 . The method of  claim 17 , wherein, subsequent to milling the rare earth oxide powder, the ratio of the maximum cross-sectional dimension to the minimum cross-sectional dimension of 90% of more of the rare earth oxide particles of the rare earth oxide powder is 2:1 or less 
     
     
         19 . The method of  claim 12 , wherein the ratio of the maximum cross-sectional dimension to the minimum cross-sectional dimension of 90% of more of the rare earth oxide particles of the rare earth oxide powder is 2:1 or less. 
     
     
         20 . The method of  claim 12 , wherein the rare earth oxide powder comprises an ytterbium oxide powder or a gadolinium oxide powder and the rare earth metal comprises an ytterbium metal or a gadolinium metal.