Crystal growth and excited-state dynamics of Eu2+ Luminescence in Eu-doped LiBaF3 single crystals

Abstract

The pure and europium doped LiBaF3 single crystals were grown by the Czochralski method. The details of the reagent preparation and the crystal growth were investigated. The different concentrations of Eu-doped powder were checked by XRD. The Eu2+ ion substitutes for Ba2+ ion in the LiBaF3 crystal. The reaction conditions were investigated to get pure LiBaF3 powder. The emission spectra showed the 4f-4f line emission peak at 359 nm and the 5d-4f emission band at around 410 nm. The spectra of Eu2+-doped crystals with different concentrates were compared and the concentration quenching was not observed up to the Eu-concentration of 2 mol%. The luminescent lifetime of 359 nm and 410 nm emissions were measured in the temperature range from 15 K to 300 K. The non-exponential decay curves at 410 nm were discussed in relation with the interaction between the excited 4f and 4f5d levels. A practical method was introduced to calculate the 4f-5d activation energy (ΔE) and the value of this energy gap was 950 cm-1. The configurational coordinate model of the LiBaF3: Eu2+ was introduced to explain the results. The mechanism of the nonradiative transitions between the excited 4f and 4f5d states was discussed.