Apparatus for producing fluoride crystal

Abstract

An apparatus for producing a fluoride crystal, which has a chamber, a window material and the like capable of dealing with the fluoride, is equipped with facilities necessary for high vacuum evacuation, and uses a crucible in which the capillary portion of the hole formed in the bottom thereof is so controlled for a seed crystal and a molten material to be easily contacted to each other; and a method for producing a fluoride crystal comprising using the apparatus. The apparatus allows the production of a single crystal of a fluoride having high quality in a extremely short time with stability.

1 . An apparatus for producing a fluoride crystal comprising a crucible having a perforation at its bottom, said apparatus producing a single crystal of fluoride by pulling down a single crystal from the crucible storing a melt of a fluoride material through the perforation of the crucible, the perforation having a length of 0 to 3 mm.  
     
     
         2 . The apparatus according to  claim 1  wherein the length of the perforation is made 0 to 2 mm.  
     
     
         3 . The apparatus according to  claim 1  wherein the crucible is made of carbon, platinum or iridium.  
     
     
         4 . The apparatus according to  claim 1  wherein the fluoride is one chosen from the group comprising calcium fluoride, barium fluoride and magnesium fluoride.  
     
     
         5 . The apparatus according to  claim 1  wherein the diameter of the perforation is in the range of 0.1 to 5 mm.  
     
     
         6 . A crucible which has, at its bottom, a perforation having a length of 0 to 3 mm.  
     
     
         7 . The crucible according to  claim 6  wherein the perforation has a length of 0 to 2 mm.  
     
     
         8 . The crucible according to  claim 6  which is for producing a single crystal by the pulling-down method.  
     
     
         9 . The crucible according to  claim 6  which is for producing a single crystal of a fluoride.  
     
     
         10 . The crucible according to  claim 6  which is made of carbon, platinum or iridium.  
     
     
         11 . A method for producing single crystals of fluorides comprising using an apparatus as described in  claim 1  for producing a single crystal of a fluoride.  
     
     
         12 . The method according to  claim 11  wherein the pulling-down speed of a seed crystal is 0.03 to 5 mm/min.  
     
     
         13 . The method according to  claim 11  wherein the pulling-down is performed while the temperature of the melt is kept higher by 0 to 100° C. than the melting point of the fluoride to be crystallized.