Sintering of lixiviated nano glass-ceramics: An original route to elaborate transparent ceramics

We report the elaboration of translucent ZnGa₂O₄ ceramics by an innovative process, the sintering by Spark Plasma Sintering (SPS) of spinel ceramic powder obtained by the lixiviation of glass-ceramics. Indeed, a selective dissolution of the silica-rich glass matrix allows isolating ZnGa₂O₄ nanocrystals embedded in the silicate glass-ceramic. This glass-ceramic is elaborated from the parent glass of composition 55 SiO₂ - 5 Na₂O - 17 ZnO - 23 Ga₂O₃ (%_mol) that undergoes a subsequent heat-treatment at 1100 °C under air leading to the crystallization of zinc gallate spinel nanocrystals with size in the 20–60 nm range. Lixiviated nanocrystals are collected and sintered by SPS to get a bulk ceramic. While the transmittance of this ceramic is only 60% at 4.5 µm, which is lower than the theoretical transmittance (82.5%), these first results are still promising and pave the way to new transparent ceramic processing route. Indeed, glass crystallization combined with selective lixiviation process is a powerful, non-conventional elaboration process that can further allow the stabilization and isolation of metastable crystalline phases with interesting functional properties.