Synthesis and investigation of magnesium–aluminum nanopowders and ceramics activated by copper

Nanopowders of two crystalline phases, magnesium–aluminum spinel (98 wt.%), and cuprite (2 wt.%) have been obtained by laser evaporation of a solid target, which is a mechanical mixture of simple oxides (MgO, Al$_2$O$_3$, CuO). These nanopowders have been used to prepare test samples of transparent Cu:MgAl$_2$O$_4$ ceramics, the IR transmission spectra of which revealed two new strong absorption bands at $\lambda_1\approx$ 1.55 (1.45) $\mu$m and $\lambda_2\approx$ 3.45 (3.03) $\mu$m, corresponding to transitions between the Stark levels $^2$E(t$_2^6$e$^3$) and $^2$T$_2$(t$_2^5$e$^4$) of Cu$^{2+}$ ions in octahedral and tetrahedral positions, respectively.