Abstract BaF 2 nanocrystals doped with 5.0 mol% Eu 3+ has been successfully synthesized via a facile, quick and efficient ultrasonic solution route employing the reactions between Ba(NO 3) 2, Eu(NO 3) 3 and KBF 4 under ambient conditions. The product was characterized via X-ray powder diffraction (XRD), scanning electron micrographs (SEM), transmission electron microscopy (TEM), high-resolution transmission electron micrographs (HRTEM), selected area electron diffraction (SAED) and photoluminescence (PL) spectra. The ultrasonic irradiation has a strong effect on the morphology of the BaF 2:Eu 3+ particles. The caddice-sphere-like particles with an average diameter of 250 nm could be obtained with ultrasonic irradiation, whereas only olive-like particles were produced without ultrasonic irradiation. The results of XRD indicate that the obtained BaF 2:Eu 3+ nanospheres crystallized well with a cubic structure. The PL spectrum shows that the BaF 2:Eu 3+ nanospheres has the characteristic emission of Eu 3+ 5 D 0– 7 F J ( J=1–4) transitions, with the magnetic dipole 5 D 0– 7 F 1 allowed transition (590 nm) being the most prominent emission line.