Gadolinium oxysulfide (Gd2O2S, GOS) doped with rare earth elements was often used as imaging materials for X-Ray imaging equipment because of its excellent properties of absorbing incident X-rays and converting them into visible light. The flat-panel detector based on the GOS phosphor screen is the core imaging component of the digital radiography. In this paper, GOS slurry was prepared to form phosphor screen by tape casting, and the influence of slurry solvents and different additives on the rheological properties of the slurry was systematically studied. Based on the results of rheological properties, the optimal solid content of the slurry and the optimal addition range of the additives, like dispersants, binders and plasticizers, were determined. The solid content of the slurry is 70%, and the best amount of dispersant is 0.5%~1% of the powder mass. The optimized dosage of binder is 4.5%~7% of the powder mass, and the best plasticizer content is 1.0~1.5 times of the binder content. Then, the GOS fluorescent layer with smooth and flat surface, uniform and controllable thickness, and good bonding ability, was successfully prepared by tape casting the optimized slurry.
In order to mitigate the dopant concentration gradient by post-growth diffusion method, high optical quality Cr2+:ZnSe ceramics had been prepared by hot-pressing method with powders being diffusion doped in a previous step, which reduced the concentration gradient down to a grain size level. A optimal combination of sintering parameters, including
temperature, pressure, dwell time, have been determined (1050°C/150MPa/2h) according to background absorption
intensity. Comparison with diffusion doped CVD-grown ZnSe showed a stronger background absorption and blueshifted
emission peak, both indicating scattering sources inside material. Micro-structure observation proved the
inference above as being residual pores and inclusions, which could be eliminated or reduced by, as suggested here,
preliminary treatment of powders and enhancement of densification pressure and dwell time.
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