Anomalous europium luminescence in LaF3

• Optical spectra and dielectric relaxation were measured for Eu2+ in LaF3.
• Bulk conductivity is directly proportional to absorption coefficient of Eu2+ bands.
• Dielectric relaxation peak of LaF3–EuF3 is attributed to ipoles Eu2+-anion vacancy.
• Broadband Eu emission at 600 is attributed to so-called anomalous luminescence.

Optical spectra (absorption, emission, excitation, decay) and dielectric relaxation were measured for divalent europium and partially for ytterbium in lanthanum fluoride crystals. Optical absorption of LaF3–Eu2+ contains not only asymmetric weakly structured band at 245 nm but also less intense bands at 330, 380 nm. Broadband Eu2+ emission at 600 nm appeared below 80 K with decay time 2.2 μs at 7.5 K. Emission at 600 nm is attributed to so-called anomalous luminescence. Bulk conductivity is directly proportional to absorption coefficient of Eu2+ bands. Dielectric relaxation peak of LaF3–EuF3 is attributed to rotation of dipoles Eu2+-anion vacancy. The long-wavelength absorption at 300–400 nm region are assigned to transitions from 4f7Eu2+ ground state to states of neighbouring fluorine vacancy.