The luminescence microspectroscopy of Pr3+-doped LiBaAlF6 and Ba3Al2F12 crystals

The combined luminescence and Raman-scattering microspectroscopy technique allows separate spectroscopic studies on several crystal phases in mixed compounds. A mixed sample of LiBaAlF6 and Ba3Al2F12 doped with Pr was studied. The Pr3+ concentration was found to be much higher in the Ba3Al2F12 phase. Several non-equivalent Pr3+ centers are present in both compounds, however, only in Ba3Al2F12 there are several non-equivalent crystallographic positions of Ba. In LiBaAlF6 non-equivalent Pr3+ centers appear because of complicated scheme for charge compensation of (PrBa3+)+. Possible reasons of Ba3Al2F12 formation in the process of Pr3+:LiBaAlF6 growth are discussed. An excess of LiF in melt is assumed to produce (LiBa+)− antisite defects as a charge compensation for (PrBa3+)+ substitution.

► During crystal growth of Pr-doped LiBaAlF6, Ba3Al2F12 was formed as a by-product.
► Microspectroscopy techniques allowed to study the two crystal phases separately.
► The Pr3+ concentration was found to be much higher in Ba3Al2F12.
► The possible reasons of Ba3Al2F12 formation while growth of Pr3+:LiBaAlF6 are discussed.