(A) study on the synthesis and scintillation properties of $Y_2O_3$-based ceramic scintillator

Abstract

The scintillator is a luminescent material that absorbs the high-energy photons, such as X-ray and gamma ray, and then emits visible light. Generally, phosphor materials could be used as scintillators, but materials with high density and atomic number are required for the detection of the high-energy radiation. One of the major applications of these scintillators is the medical CT-scanner. Single-crystal scintillators currently used in detectors in commercial CT scanners are Tl-activated CsI and self-activated $CdWO_4$. But, these single crystal scintillators have high value of afterglow and low light output, respectively. Ceramic scintillators are developed to obtain proper scintillation properties for specific application. Properties of ceramic scintillators can be adjusted by the composition variation of scintillators. However, the disadvantage of ceramic scintillator is the difficult production process of transparent ceramics. In this study, a novel process, which consists of GNP powder synthesis, subsequent hot pressing, and annealing step were developed to fabricate the transparent $(Y,Gd)_2O_3$ ceramic scintillator. Effect of the characteristics of synthesized powder and the sintering conditions on the luminescent properties of the transparent ceramic scintillator was discussed. 1. $(Y,Gd)_2O_3$ transparent ceramic scintillator was fabricated using the nanometer-sized powders which were synthesized by GNP method, subsequent hot pressing and annealing step. GNP method provided single phase, fully solid solution of $(Y,Gd)_2O_3$, high purity, high specific surface area, nanometer size powder. Residual elements in as-combusted powder were by multi-step heat-treatment at vacuum and air atmosphere. In sintering step, pressure schedule of hot pressing was optimized to enhance the transmittance. Microstructure shows near full dense structure but only few pores were observed in the grain boundary and corner. Luminescent property of $(Y,Gd)_2O_3$:Eu ceramic scin...