SCINTILLATION COMPOUND INCLUDING A RARE EARTH ELEMENT AND A PROCESS OF FORMING THE SAME
A scintillation compound can include a rare earth element that is in a divalent (RE 2+ ) or a tetravalent state (RE 4+ ). 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 (M 3+ ) may be replaced by RE 4+ and a metal element in a divalent state (M 2+ ). In another embodiment, M 3+ may be replaced by RE 2+ and M 4+ . In a further embodiment, M 2+ may be replaced by a RE 3+ and a metal element in a monovalent state (M 1+ ). 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.
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.