Microstructure, absorption and luminescence of Co2+:ZnAl2O4 transparent ceramics: Effect of the sintering additive

Transparent ceramics of cobalt-doped zinc aluminium spinel (gahnite), Co²⁺:ZnA₂O₄, are synthesized by hot pressing at 1520 °C for 4 h in the presence of zinc fluoride, ZnF₂, as a sintering additive. The effect of the ZnF₂ content (3–10 wt%) on the microstructure, Raman spectra, optical absorption and luminescence of ceramics is studied. The ceramics feature clean grain boundaries, the absence of pores and a narrow grain size distribution (mean grain size: 70-100 μm) resulting in high in-line transparency close to the theoretical limit. The obtained ceramics are suitable for fabrication of saturable absorbers of erbium lasers.