Rare Earth Oxyfluoride Sintered Body And Method For Producing Same

Abstract

A sintered rare earth oxyfluoride compact is composed of LnaObFc (wherein Ln is a rare earth element; and a, b, and c each independently represent a positive number, provided that they are not equal to each other) or Ca-stabilized LnOF as a primary phase and LnOF unstabilized with Ca as a secondary phase. The intensity ratio of the XRD peak of the (018) or (110) plane of the unstabilized LnOF to the highest XRD peak of LnaObFc is preferably 0.5% to 30%.

What is claimed is: 
     
         1 . A sintered rare earth oxyfluoride compact comprising:
 Ln a O b F c , wherein Ln is a rare earth element, and a, b, and c each independently represent a positive number that are not equal to each other; or   Ca-stabilized LnOF as a primary phase and LnOF unstabilized with Ca as a secondary phase.   
     
     
         2 . The sintered rare earth oxyfluoride compact according to  claim 1 , wherein the intensity ratio of the XRD peak of the (009) or (107) plane of the unstabilized LnOF, wherein Ln is a rare earth element, to the highest XRD peak of the Ca-stabilized LnOF is 0.5% to 10%. 
     
     
         3 . The sintered rare earth oxyfluoride compact according to  claim 2 , wherein the unstabilized LnOF as the secondary phase are present in the boundaries between the grains of the Ln a O b F c  or Ca-stabilized LnOF as the primary phase. 
     
     
         4 . The sintered rare earth oxyfluoride compact according to  claim 1 , having a three-point flexural strength of 50 to 300 MPa. 
     
     
         5 . The sintered rare earth oxyfluoride compact according to  claim 1 , having a surface roughness Ra, as specified in JIS B0601, of 1 μm or smaller. 
     
     
         6 . The sintered rare earth oxyfluoride compact according to  claim 1 , having an inflection-point of dimensional change with temperature occurring at a temperature ranging from 200° to 800° C. 
     
     
         7 . The sintered rare earth oxyfluoride compact according to  claim 1 , wherein the primary phase has an average grain size of 1 to 200 μm, the secondary phase has an average grain size of 0.1 to 5 μm, and the average grain size of the primary phase is larger than that of the secondary phase. 
     
     
         8 . The sintered rare earth oxyfluoride compact according to  claim 1 , wherein the Ca-stabilized LnOF shows a cubic crystal phase at 25° C. 
     
     
         9 . The sintered rare earth oxyfluoride compact according to  claim 8 , wherein the Ca-stabilized LnOF is YOF,
 the reflection peak from the (111) plane of the cubic YOF observed at a 2θ angle around 28.8° is the highest in powder XRD, and the reflection peak intensity from the (006) plane of rhombohedral YOF observed at a 2θ angle around 28.4° is 15 or less relative to the intensity of the highest peak being taken as 100.   
     
     
         10 . The sintered rare earth oxyfluoride compact according to  claim 2 , wherein the unstabilized LnOF as the secondary phase are present in the boundaries between the grains of the Ln a O b F c  or Ca-stabilized LnOF as the primary phase.