Tunable luminescence of Eu3+‐activated CaWO4 nanophosphors via Bi3+ incorporation

Abstract A series of CaWO 4 :3Eu 3+ : x Bi 3+ ( x = 2, 5, 7 and 10 at.%) nanophosphors was prepared through the efficient low‐temperature ethylene glycol route. Their structural, as well as photophysical, properties were studied. X‐ray diffraction analysis and a X‐ray photoelectron spectroscopy survey confirmed that the Bi 3+ and Eu 3+ ions incorporated perfectly into Ca 2+ and without disturbing the lattice. The samples exhibited almost spherical morphology with average particle sizes from 10 to 30 nm. For the nanoparticles, Fourier transform infrared spectroscopy featured broad absorption bands around 871 and 778 cm −1 that were due to antisymmetric stretching, whereas a peak at 435 cm −1 was assigned to antisymmetric bending vibrations of the bonds in [WO 4 2− ] clusters. The nanophosphors showed orange‐red luminescence, which was further tuned to red by incorporation of sensitizer Bi 3+ ions. This colour tuning of the nanoparticles is described in the context of energy transfer from the WO 4 2− group to sensitizer Bi 3+ and activator Eu 3+ ions under 394 nm excitation. A CIE diagram supports this colour tunability.