LiBa12(BO3)7F4 (LBBF) crystals doped with Eu3+, Tb3+, Ce3+: structure and luminescence properties

The luminescent properties of single crystals and polycrystalline samples of LiBa12(BO3)(7)F-4 (LBBF) doped and co-doped with Eu3+, Tb3+, and Ce3+ have been studied in order to disclose their potential for application in white light-emitting diodes. Deciphering of LBBF:Eu3+ crystal structure (P4(2)/mbc) makes it possible to determine the scheme of heterovalent isomorphic substitution 3Ba(2+) <- 2Eu(3+) + , - vacancy in barium sites. Luminescent properties of LBBF crystals co-doped with Eu3+, Tb3+, Ce3+ and Eu3+, Tb3+ are compared. Both crystals demonstrate the luminescence close to day light with CIE coordinates and correlated color temperature (0.280; 0.305), 9232 K for LBBF:Eu3+,Tb3+,Ce3+ and (0.353; 0.390), 4849 K for LBBF:Eu3+,Tb3+ at 300 K at 370 nm excitation. The study of polycrystalline samples LBBF:Ce3+, LBBF:Tb3+, and LBBF:Eu3+, using X-ray diffraction, shows that the homogeneity regions of solid solutions differ significantly. In solid solutions LBBF:Tb3+ and LBBF:Eu3+, a gradual change in symmetry in the tetragonal -> orthorhombic -> tetragonal series takes place as the concentration of the dopant increases. When excited at a wavelength 395 nm, LBBF:Eu3+ samples with the content of Eu3+ 0.5 wt% and 2 wt% demonstrate intense red light with a high quantum yield of 63 and 60%, respectively, which allows them to be used as red components of composite phosphors for white LEDs.

Automated summary

The luminescent properties of LiBa12(BO3)(7)F-4 (LBBF) single crystals and polycrystalline samples doped and co-doped with Eu3+, Tb3+, and Ce3+ were investigated for their potential use in white light-emitting diodes. The crystal structure of LBBF:Eu3+ was determined, allowing for the identification of a heterovalent isomorphic substitution in barium sites. The luminescent properties of LBBF crystals co-doped with Eu3+, Tb3+, Ce3+ and Eu3+, Tb3+ were compared, with both samples exhibiting a similar luminescence close to daylight.