We report an upconverting nanomaterial composition, [Y₂O₃; Yb (2%), Er (1%)], that converts both X-ray and high-fluence NIR irradiation to visible light. This composition is compared to a higher Yb³⁺ doped composition, [Y₂O₃; Yb (10%), Er (1%)], that displays diminished visible X-ray scintillation, but shows enhanced red wavelength centered upconversion emission. These nanocrystals have been characterized by TEM, X-ray diffraction, power-dependent upconversion luminescence, and X-ray scintillation spectroscopy. We further demonstrate that lithium ion doping of the [Y₂O₃; Yb (2%), Er (1%)] nanoscale composition leads to enhanced X-ray and NIR excited emission intensities through the production of nanoparticles that feature slightly enhanced sizes and increased crystallinity.