Nanocrystalline ZrO2 ceramics with idealized macropores

Macroporous nanocrystalline 4 mol% yttria-stabilised zirconia ceramics were fabricated by a novel colloidal processing technique, using a commercially available nano-powder with modified surface and polymethylmethacrylate (PMMA) sacrificial templates as starting materials. Monolithic bodies obtained by gel-casting of nano-powder/PMMA-templates suspensions presented remarkably homogeneous microstructures after sintering characterized by grain size <200 nm, macropore diameter around 1 μm, and closed porosity varying between 10 and 20%. The achieved microstructure highly resembles the high burn-up structure of highly irradiated light water reactor UO2 fuel, the properties of which are aimed to be assessed via the present model material. The sintering behaviour of bodies with or without macropores was compared. The sintering activation energy for dense, PMMA-free bodies was found to be as low as 157 kJ/mol suggesting grain boundary diffusion mechanism for mass transport. For the porous material, the measured sintering activation energy was even lower (129 kJ/mol).