Transparent phosphate glass ceramics co-doped with Er 3+ and Yb 3+ in the system P 2 O 5 Li 2 OCaF 2 TiO 2 were successfully synthesized by melt-quenching and subsequent heating. Formation of the nanocrystals was confirmed by X-ray powder diffraction. Judd–Ofelt analyses of Er 3+ ions in the precursor glasses and glass ceramics were performed to evaluate the intensity parameters Ω 2,4,6 . Under 975nm excitation, intense upconversion (UC) and infrared emission (1545nm) were observed in the glass ceramics by efficient energy transfer from Yb 3+ to Er 3+ . The luminescence processes were explained and the emission cross section was calculated by Fuchtbauer–Ladenburg (F–L) formula. The results confirm the potential applications of Er 3+ /Yb 3+ co-doped glass ceramics as laser and fiber amplifier media.