Investigation of the imaging characteristics of the Gd2O3:Eu nanophosphor for high-resolution digital X-ray imaging system

For possible applications in high-resolution medical image systems, we manufactured a Eu3+-doped Gd2O3 nanophosphor using the low-temperature solution combustion method, and evaluated its performance as an image sensor. The structural and optical characteristics of the fabricated nanophosphor were investigated using field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), photoluminescence spectrum (PL), and luminescence decay time measurements. From the FE-SEM and XRD results, we established that the fabricated nanophosphor was formed of spherical particles of about 30–40 nm, and confirmed that the particles agglomerated as the sintering temperature increases. From PL spectra, a strong peak appeared near 611 nm, and the luminescent intensity was seen to be affected by the doping concentration of Eu. Gd2O3:Eu nanophosphor particles have shown the highest luminescent efficiency at a Eu concentration of 5 wt%. In the luminescent decay time measurements, the mean decay time was about 2.3–2.6 ms, about two times longer than that of the general bulk phosphor, and affected by the of Eu-doping concentration. For the investigation of the imaging characteristics of the fabricated nanophosphor, we connected the Gd2O3:Eu nanophosphor film to a commercial CMOS image sensor, obtained the X-ray images and evaluated the modulation transfer function (MTF) as a function of the Eu concentration. We were able to obtain high-resolution X-ray images and found that the Eu concentration also influenced the imaging characteristics.