Synthesis and study of Fe2+ : MgAl2O4 ceramics for active elements of solid-state lasers

The results of pioneering studies on preparation of highly transparent Fe²⁺ : MgAl₂O₄ ceramics from powders synthesised in a laser torch are presented. This ceramics with a high transparency in the near-IR spectral region is synthesised for the first time at a low temperature (1300 °C) and a short (1 h) sintering time. It is found that, as the iron oxide concentration increases from 0.1 to 5 wt %, the concentration of Fe³⁺ ions in samples decreases to zero. It is shown that the samples of Fe²⁺ : MgAl₂O₄ ceramics contain the second phase (MgO)_0.91(FeO)_0.09 with a concentration of several percent, which considerably decreases transmission coefficient T in the visible region. At the same time, the T coefficient increases with increasing wavelength λ due to a decrease in Rayleigh scattering and almost reaches the theoretical value 85.6% for λ = 4 μm. The absorption cross section σ for Fe²⁺ ions at λ = 2 μm is determined to be (1.66 ± 0.14) × 10^-20 cm².