Translucent γ-AlOOH and γ-Al2O3 glass-ceramics using the cold sintering process

Abstract

Cold Sintering Process has been applied to hydroxide precursors Al(OH) 3 , xH 2 O to promote in situ reactive sintering. The application of sintering temperatures < 400 °C led to the release of OH groups and partial crystallization into boehmite γ-AlOOH. This latter step is accompanied by a densification stage leading to the production of dense translucent pellet. From skeletal density measurements, it appears that not all the pellet is composed of crystalline phase, but contains a mix of amorphous and crystalline phase. The presence of amorphous phase seems to favor the mechanical stability of the samples made of the inter- mediate boehmite phase, which is brittle due to its oriented layer structure. Further heat treatment in an oven at 500 °C induces the transformation of boehmite into γ-Al 2 O 3 . Here we demonstrate the possibility to produce optically translucent ceramics of low temperature stability gamma alumina structure.