Scintillation compound including a rare earth element and a process of forming the same

Abstract

A scintillation compound can include a rare earth element that is in a divalent (RE2+) or a tetravalent state (RE4+). The scintillation compound can include another element to allow for better change balance. The other element may be a principal constituent of the scintillation compound or may be a dopant or a co-dopant. In an embodiment, a metal element in a trivalent state (M3+) may be replaced by RE4+ and a metal element in a divalent state (M2+). In another embodiment, M3+ may be replaced by RE2+ and M4+. In a further embodiment, M2+ may be replaced by a RE3+ and a metal element in a monovalent state (M1+). The metal element used for electronic charge balance may have a single valance state, rather than a plurality of valence states, to help reduce the likelihood that the valance state would change during formation of the scintillation compound.

What is claimed is: 
     
         1 . A scintillator crystal comprising the formula Lu (2−y) Y (y−z−x) Ce x M z Si (1−v) M′ v O 5  wherein:
 M represents a divalent alkaline-earth element selected from the group consisting of Ca, Mg, Sr, or Ba; 
 M′ represents a trivalent element selected from the group consisting of Al, Ga, Sc, or In; 
 (z+v) is greater than or equal to 0.0001 and lower than or equal to 0.2; 
 z is greater than 0 and lower than or equal to 0.2; 
 v is greater than or equal to 0 and lower than or equal to 0.2; 
 x is greater than or equal to 0.0001 and less than 0.1; and 
 y is from (x+z) to 1. 
 
     
     
         2 . The scintillator crystal of  claim 1 , wherein z is greater than or equal to 0.00003. 
     
     
         3 . The scintillator crystal of  claim 1 , wherein z is greater than or equal to 0.0001. 
     
     
         4 . The scintillator crystal of  claim 1 , wherein z is lower than or equal to 0.1. 
     
     
         5 . The scintillator crystal of  claim 1 , wherein (z+v) is greater than or equal to 0.0002. 
     
     
         6 . The scintillator crystal of  claim 1 , wherein (z+v) is less than or equal to 0.05. 
     
     
         7 . The scintillator crystal of  claim 1 , wherein x is the sum of Ce 3+  and Ce 4+ . 
     
     
         8 . The scintillator crystal of  claim 1 , wherein y is greater than or equal to 0.08 and less than or equal to 0.3. 
     
     
         9 . The scintillator crystal of  claim 1 , wherein cerium represents 0.005 mol % to 20 mol % of all the rare earths in the scintillator crystal. 
     
     
         10 . The scintillator crystal of  claim 1 , wherein the divalent alkaline earth element is present in a proportion from 0.0025 mol % to 15 mol %. 
     
     
         11 . The scintillator crystal of  claim 1 , wherein the proportion of M′ is between 0.005 mol % to 25 mol % of a sum of the moles of silicon and of the trivalent metal codopant. 
     
     
         12 . The scintillation crystal of  claim 7 , wherein a ratio of the rare earth element in the tetravalent state to the dopant M is at least approximately 1:90. 
     
     
         13 . The scintillator crystal of  claim 1 , wherein M is Ca. 
     
     
         14 . A scintillator crystal comprising the formula Lu (2−y) Y (y−z−x) Ce x Ca z SiO 5  wherein:
 (z+v) is greater than or equal to 0.0001 and lower than or equal to 0.2;   z is greater than 0 and lower than or equal to 0.2;   v is greater than or equal to 0 and lower than or equal to 0.2;   x is greater than or equal to 0.0001 and less than 0.1; and   y is from (x+z) to 1.   
     
     
         15 . The scintillator crystal of  claim 14 , wherein the scintillation crystal has an afterglow of less than 200 ppm after 100 ms relative to the intensity measured during an X-ray irradiation. 
     
     
         16 . The scintillator crystal of  claim 14 , wherein the scintillation material's absorbance at a wavelength of 357 nm is less than the scintillation material's absorbance at 280 nm. 
     
     
         17 . An ionizing particle detector comprising the material of  claim 12  and a photosensor. 
     
     
         18 . An apparatus of one of an ionizing particle detector, a luminescence emitter, or a medical imaging apparatus comprising:
 a scintillator crystal within one of the ionizing particle detector, the luminescence emitter, or the medical imaging apparatus comprising the formula Lu (2−y) Y (y−z−x) Ce x M z SiO 5  wherein:
 M represents a divalent alkaline-earth element selected from the group consisting of Ca, Mg, Sr, or Ba; 
 z is greater than 0 and lower than or equal to 0.2; 
 x is greater than or equal to 0.0001 and less than 0.1; and 
 y is from (x+z) to 1. 
   
     
     
         19 . The scintillator crystal of  claim 18 , wherein M is Ca. 
     
     
         20 . The scintillator crystal of  claim 18 , wherein y is greater than or equal to 0.08 and less than or equal to 0.3.