Hot-Pressing Method to Consolidate Gd3(Al,Ga)5O12:Ce Garnet Scintillator Powder for use in an X-ray CT Detector

We have developed a hot-pressing method for consolidating garnet scintillator powder of composition Gd-3(Al,Ga)(5)O-12:Ce. Thermodynamic analysis revealed that gallium oxide, which was a constituent of the garnet scintillator powder, would react with the graphite mold beginning at 950 degrees C and would be reduced to gallium metal. To prevent this reaction during hot-pressing, a reaction barrier material was placed between the graphite mold and the scintillator powder. As for the reaction barrier material, 3GdAlO(3)-Al2O3 powder calcined at 1100 degrees C was found to be suitable because the material provided two important characteristics: the same thermal expansion coefficient as the scintillator material and good sinterability. The Gd-3(Al,Ga)(5)O-12:Ce garnet scintillator powder was hot pressed at 1475 degrees C for 4h in vacuum, followed by annealing at 1300 degrees C for 4h in oxygen atmosphere. The thus obtained garnet scintillator successfully satisfied the necessary requirements for use in an X-ray computed tomography detector.