Grain boundary evolution on sintering in yttria (8 mol%)-stabilized zirconia assisted by one or two driving forces

Sintering of yttria (8 mol%)–zirconia ceramics assisted by one or two driving forces was performed using nanosized precursors hydrothermally synthesized.Two monophasic precursors, both containing 8 mol% of yttria, were hydrothermally synthesized from amorphous zirconia–yttria co-precipitate and from a mechanical mixture of amorphous zirconia with crystalline yttria, respectively.Two diphasic precursors, characterized by the same yttria content (8 mol%), were obtained mixing in an equal molar ratio two hydrothermally synthesized powders with yttria content of 2 and 14 mol%, respectively.By applying a same pressureless heating schedule, the different precursors, previously pressed by cold isostatic pressing, were sintered and characterized.The diphasic precursors assisted on sintering by the double driving force, the surface area and the composition gradient, show an exaggerated formation of the grain boundary interfaces in comparison to that of the monophasic precursors sintered in the presence of the single driving force, the surface area.