[en] The effect of chemical composition, average grain size and phases content on fracture toughness and bending strength of Y-TZP (tetragonal zirconia polycrystals with Yttria additions) has been studied. Samples have been prepared from zirconia powders coprecipitated with 2 and 3 mol% Yttria, and sintered according to different routes in order to promote different grain size specimens. All samples reached higher than 97% theoretical and density and grain sizes ranging from 0,24 to 0,57 μm. Fracture toughness determinations have been done by two different methods: notched beam and Vickers indentation; for the latter several available mathematical models have been considered for analysis. Four point bending strength measurements have been carried out on samples sintered under various conditions following the variation of tetragonal phase content before and after testing. The susceptibility of tetragonal-to-monoclinic phase transformation of one 3 mol% Yttria specimen under thermal neutron fluxes has also been studied. (author)