The Fabrication of Monoclinic Gd $_{2}$O $_{3}$ Transparent Microspheres and Scintillator Array via Laser Heating

Monoclinic Gd
₂
O
₃
transparent ceramics with spherical shape were successfully fabricated by a laser heating method. A simple model was used to describe the heating depth and cooling rate during the laser scanning process. The XRD analysis shows that these microspheres exhibit monoclinic structure which is room temperature thermodynamically unstable but kinetically possible due to the fast cooling rate. The SEM images show that these micro-spheres are polycrystalline and composed of randomly oriented Gd
₂
O
₃
grains about 10 μm in particle diameter. No cracks, pores or secondary phase were observed at the grain boundary or inside the grains. A close-packed Gd
₂
O
₃
spheres single layer was designed and prepared, and the in-line transmittance of this layer is about 44% in the visible light range. Pore-free monoclinic Gd
₂
O
₃
can be transparent due to the slight difference between its ordinary and extraordinary refractive index (n e and n o). Another reason for its transparency is the small amount of grain boundaries though which light pass. Medical radiograph needs scintillators with small volume size (to increase the image lateral resolution and minimize optical cross-talking) and good transparency (to avoid severe light scattering and increase signal intensity). Transparent ceramic spheres may provide the possibility to meet those criterions.