Zirconia is one of the most important ceramic materials because of the large range of industrial applications (catalysis, coatings, spacecraft shielding, paint additives, oxygen sensors, fuel cells, nuclear fuel matrix, alternative high permitivity material to replace silicon oxide as gate dielectric in MOS devices...). It is now well established that a monoclinic to tetragonal phase transition occurs in this material. This transition can for instance be trigged by the grain size. The mechanism of this phase transition is now clearly understood. Zirconia can be considered a textbook example for describing these effects. In this paper, we will discuss the mechanism of the tetragonal to monoclinic martensitic phase transition induced by irradiation within the Landau theory framework, pointing out the peculiar effects related to nanostructuration of this material by irradiation. Such a work is an illustrative example of structural modification of solids induced by irradiation.