It is interesting to note that the samples with tetragonal zirconia AP-Zt and AP-Zt-HP are attractive in terms of properties, even without the presence of glass phase or alumina nanoparticles. AP-Zt has much weaker properties than the standard AP ng composition, probably because of its high porosity. The application of a higher sintering stress (AP-Zt-HP) reduces the porosity and finally leads to properties quite close to AP ng . This composition has the advantage of simpler shaping, because without addition of nanoparticles and glass phase, and is potentially more resistant to creep because without glass at the grain boundaries, creep being a critical issue for high temperature applications.