(Invited) Laser Sintering of Polycrystalline Ceramic Scintillators: The Case Study of YAG:Ce

Scintillators are sensors used for the detection and measurement of ionizing radiation that find application in numerous strategic fields. Among the many possible scintillator forms, polycrystalline ceramics have received increasing attention due to advantages over single crystals, including faster and lower cost fabrication methods, higher homogeneity of the dopant, greater shape control, and easier fabrication of materials with high melting temperatures. Polycrystalline ceramic scintillators are commonly fabricated by high temperature vacuum sintering [1] and more recently by spark plasma sintering [2,3]. However, additional high-cost processing by means of hot isostatic pressing is many times necessary especially because it has been shown that the use of sintering aids is detrimental to scintillation performance [4]. On the other hand, despite the advantages of extremely short sintering times and high heating rates, laser sintering remains mostly unexplored as a viable method to fabricate these materials. To date, the only polycrystalline ceramic scintillator fabricated by this method was Bi 4 Ge 3 O 12 (BGO) [5-7]. In this work, the fabrication of Y 3 Al 5 O 12 :Ce (YAG:Ce) polycrystalline ceramic scintillators by laser sintering is evaluated against a Czochralski-grown single crystal in terms of the microstructure characteristics as well as luminescent and scintillating properties. YAG:Ce powders were prepared by a polymeric precursor method using Y(NO 3 ) 3 ×6H 2 O, AlCl 3 ×6H 2 O, and CeH 8 O 18 N 8 as metal precursors such that the concentration of Ce substituting for Y was 0.1 and 0.3 %. Metal precursors were dissolved in citric acid:distilled water solutions at 70 o C under continuous stirring followed by the addition of ethylene glycol. The final solution was heated up to 100 o C to eliminate water and promote polymerization. The resultant material was pre-calcined at 600 o C for 5 h followed by calcination at 1000 o C for 6 h, and then pressed into 4 mm dia. x 1.2 mm thick pellets. Laser sintering was executed using a Coherent GEM-100L CO 2 laser generating a power density of ~3.3 W/mm 2 for 90 s. The microstructure was characterized by means of density, X-ray diffraction (XRD), scanning electron microscopy (SEM), attenuated total reflectance Fourier transform infrared spectroscopy (ATR FTIR), and X-ray absorption near edge structure (XANES) measurements. Optical transparency and luminescence were evaluated in terms of UV-visible transmittance,