Novel transparent MgGa₂O₄ and Ni²⁺-doped MgGa₂O₄ ceramics

In this study we fabricated, for the first time, magnesium gallate (MgGa₂O₄, a partially inverted spinel) transparent ceramics, both undoped and doped with 1 at% Ni. The specimens were derived from in-house prepared powder, with a crystallite size of ~10 nm (by wet chemistry) and densified by pulsed electric current sintering (PECS; peak temperature 950 ℃ for 90 min). Densification levels of 99.84% and 99.52% of theoretical density were attained for doped and undoped materials, respectively. Doping with Ni was seen to marginally improve the densification level. Quite transparent specimens were produced: the best showing transmission of ~89% of the theoretical level (thickness t = 0.85 mm). The absorption spectra revealed that the dopant was accumulated as Ni²⁺ in the octahedral sites of the lattice, as occurs in single-crystal specimens. After excitation at 980 nm, the doped disks exhibited a wide fluorescence band centered at 1264 nm.