Zirconium oxide and the crystallinity hallows

Zirconium oxide is one of the most promising ceramic materials as it finds applications in several high-level technological fields, ranging from biomedicine to sensing. Zirconium oxide is characterized by showing very uncommon properties for being a ceramic substrate, such as a certain plastic behavior once subjected to mechanical stress, a naturally occurring phase transformation toughening, as well as a dramatic sensibility toward water-induced aging (if hydrothermally treated). In general, all these properties are strictly correlated with the tetragonal-to-monoclinic interphase transformation and, consequently, driven by the stabilization of the tetragonal phase. Hence, in this study, a summary of the main relevant principles guiding zirconium oxide interphase transformations is proposed, highlighting the important role of stabilizers and the correlation between microstructure and doping. A particular emphasis has been dedicated to the thermodynamics behind these phenomena.