Ferroelastic Nanomaterials

Ferroelastics are the materials where the order parameter is mechanical deformation that spontaneously appears at transition temperature. As it was mentioned in Chap. 1, Aizu [74, 75] was the first who gave the formal definition of ferroelasticity as the property that can exist by itself in the materials which are neither ferroelectrics nor ferromagnets. 

Spontaneous deformation appears at temperature lowering as a result of structural phase transition from paraelastic phase to less symmetric ferroelastic phase. In this case, the breaking of such crystal into domains corresponds to elastic energy minimum. 

The microstructure of ZrOaiYaOs (YSZ) sample fabricated by the above method is reported in Fig. 2.53. It follows from the figure that the sample is dense with 

2 The Peculiar Physical Properties of Nanosized Ferroics (Nanoferroics) 

The comparison of grain sizes for YSZ samples on mono- and poly crystalline AI2O3 substrates are represented in Fig. 2.55. One can see that microstructure is independent of the substrate type for the samples sintered at T 800 °C. At T 800 °C the fast growth of grain sizes begins in the films on poly crystalline substrate, while for monocrystalline one this growth starts at T 1,000 Such behavior could be attributed to different rates of YSZ nucleation, which could be faster for polycrystalline substrate. 

---