Ceramic scintillator array, method for manufacturing same, radiation detector and radiation inspection device
A ceramic scintillator array of an embodiment includes: a plurality of scintillator segments each composed of a sintered compact of a rare earth oxysulfide phosphor; and a reflective layer interposed between the scintillator segments adjacent to each other. The reflective layer contains a transparent resin and reflective particles dispersed in the transparent resin. The reflective particles contain titanium oxide and at least one inorganic substance selected from the group consisting of alumina, zirconia, and silica. A glass transition point of the transparent resin is 50° C. or higher, and a thermal expansion coefficient of the transparent resin at a temperature higher than the glass transition point is 3.5×10 −5 /° C. or less.
1. A ceramic scintillator array comprising:
a plurality of scintillator segments each composed of a sintered compact of a rare earth oxysulfide phosphor; and
a reflective layer interposed between the scintillator segments adjacent to each other to integrate the plurality of scintillator segments, the reflective layer containing a transparent epoxy resin and reflective particles dispersed in the transparent epoxy resin, wherein the transparent epoxy resin is a two-component epoxy resin curable at room temperature;
wherein the reflective particles contain titanium oxide and at least one inorganic substance selected from the group consisting of alumina, zirconia, and silica; and
wherein a glass transition point of the transparent epoxy resin is 60° C. or higher, and a thermal expansion coefficient of the transparent epoxy resin at a temperature higher than the glass transition point is 2.5×10 −5 /° C. or less.
2. The ceramic scintillator array according to claim 1 , wherein the ceramic scintillator array is configured to minimize a change amount in any of a pitch of the ceramic scintillator segments, a warpage of the ceramic scintillator array, and an outside dimension of the ceramic scintillator array, whereby the change amount, after the ceramic scintillator array is stored in a packed state for one month in an atmosphere at a temperature of 50° C. and a relative humidity RH of 80%, is 0.02 mm or less.
3. The ceramic scintillator array according to claim 1 , wherein the ceramic scintillator array is configured to minimize a decrease in light output of the ceramic scintillator array, wherein the decrease in light output, measured by an X-ray exposure amount corresponding to 10 years of operation, is within 25%.
4. The ceramic scintillator array according to claim 1 , wherein a molecular structure of the transparent epoxy resin has a cyclo structure without any double bonds.
5. The ceramic scintillator array according to claim 1 , wherein the transparent epoxy resin has an aliphatic skeleton.
6. The ceramic scintillator array according to claim 1 , wherein the reflective layer contains, by mass ratio, 15% or more and 60% or less of the transparent epoxy resin and 40% or more and 85% or less of the reflective particles.
7. The ceramic scintillator array according to claim 1 , wherein the rare earth oxysulfide phosphor has a composition expressed by a general formula RE 2 O 2 S:Pr,
wherein RE is at least one element selected from the group consisting of Y, Gd, La, and Lu, and wherein a content of Pr, relative to a content of RE 2 O 2 S, is 0.001 mol % or more and 10 mol % or less.
8. The ceramic scintillator array according to claim 7 , wherein the rare earth oxysulfide phosphor contains a gadolinium oxysulfide phosphor containing Pr as an activator.
9. The ceramic scintillator array according of claim 1 , wherein the reflective particles have a bimodal particle size distribution, wherein a first peak in the bimodal particle size distribution is 200 nm or more and 350 nm or less, and wherein a second peak in the bimodal particle size distribution is 750 nm or more and 1000 nm or less.
10. The ceramic scintillator array according to claim 1 , wherein a reflection efficiency of the reflective layer with respect to light having a wavelength of 512 nm is 90% or more.
11. A radiation detector comprising the ceramic scintillator array according to claim 1 .
12. A radiation inspection device comprising the radiation detector according to claim 11 .
13. A method for manufacturing the ceramic scintillator array according to claim 1 , the method comprising:
applying or filling a mixture of the reflective particles and an uncured material of the transparent two-component epoxy resin, having an absolute viscosity, measured in units of Pascal-second (Pa·s), of 0.2 Pa·s or more and 1 Pa·s or less, between the plurality of scintillator segments arrayed to constitute the ceramic scintillator array; and
curing the mixture at room temperature to form the reflective layer to thereby integrate the plurality of scintillator segments.
14. The method according to claim 13 , wherein the transparent two-part epoxy resin has a total light transmittance of 85% or more.