Luminescence of Ce3+ activated NaCaPO4 under VUV–UV and X-ray excitation

A series of Na1+xCa1−2xCexPO4 phosphors were prepared by a high-temperature solid-state reaction method. Excitation spectra in VUV–UV range, emission spectra under VUV–UV and X-ray excitation, and luminescence decays were investigated for samples with different doping concentrations at RT and 14 K. Seven excitation bands and two emission bands due to f–d transitions of Ce3+ were found in the spectra. The observed spectroscopic properties may relate to multi-site occupancies of Ce3+ in NaCaPO4 but Ce3+ ions at different sites emit at similar wavelengths or the emission only occurs from the lowest energy site due to the efficient energy transfer between different Ce3+ sites.

► Luminescence of Na1+xCa1−2xCexPO4 under VUV–UV and X-ray excitation was investigated.
► Seven excitation bands and two emission bands due to f–d transitions of Ce3+ were observed.
► Ce3+ ions may occupy multi-sites but they emit at similar wavelengths or only from the lowest energy site.