LiBa 12 (BO 3 ) 7 F 4 (LBBF) crystals doped with Eu 3+ , Tb 3+ , Ce 3+ : structure and luminescence properties.

The luminescent properties of single crystals and polycrystalline samples of LiBa 12 (BO 3 ) 7 F 4 (LBBF) doped and co-doped with Eu 3+ , Tb 3+ , and Ce 3+ have been studied in order to disclose their potential for application in white light-emitting diodes. Deciphering of LBBF:Eu 3+ crystal structure ( P 4 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 Eu 3+ , Tb 3+ , Ce 3+ and Eu 3+ , Tb 3+ 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:Eu 3+ ,Tb 3+ ,Ce 3+ and (0.353; 0.390), 4849 K for LBBF:Eu 3+ ,Tb 3+ at 300 K at 370 nm excitation. The study of polycrystalline samples LBBF:Ce 3+ , LBBF:Tb 3+ , and LBBF:Eu 3+ , using X-ray diffraction, shows that the homogeneity regions of solid solutions differ significantly. In solid solutions LBBF:Tb 3+ and LBBF:Eu 3+ , 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:Eu 3+ samples with the content of Eu 3+ 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.