Up- and down-conversion luminescence in the oxyfluoride glass ceramics containing Ba2+1.5xYb1−xF7:Tb3+ nanocrystals

► Oxyfluoride glass ceramics containing Ba2+1.5xYb1−xF7:Tb nanocrystals were prepared. ► The precipitated crystal phase changed from BaF2 to Ba2+1.5xYb1−xF7. ► Strong up-conversion and down-conversion emissions were observed and interpreted.