|Apr 25, 2019|
Crack propagation is asymmetric in polar materials(Nanowerk News) Fracture physics is a central field of study in materials science. In the case of piezoelectric materials, due to their ability to generate strains if subjected to a voltage and vice versa, microcracks are usual and shorten the lifespan of the devices in which they are used.
|Researchers therefore look for ways in which fractures can be prevented, although sometimes they can also be used to our advantage. For instance, controlled cracking has been proposed as a mechanism for device nanopatterning.|
|Fracture fronts concentrate the maximum deformation that a solid can withstand, so flexoelectricity (polarization induced by deformation gradients) plays a key role.|
|A recent study published in Physical Review Letters ("Flexoelectric Fracture-Ratchet Effect in Ferroelectrics") shows that crack-generated flexoelectricity acts facilitating or hampering crack propagation, depending on the polarization axis of the material.|
|The team shows how, due to flexoelectricity, cracks in ferroelectrics (switchable polar materials) propagate more easily in the polar direction than in the opposite. (Image: ICN2)|
|This study has a couple of important implications. It is the first to experimentally demonstrate that crystal fracture is not symmetric: cracks travelling in the polar direction are measurably longer than those traveling against.|
|Second, since the polarity of a ferroelectric can be switched by voltage, voltage can serve as a tool to manage the propagation of cracks in polar materials, either to mitigate fatigue (the weakening and subsequent breakage of the material), or to promote fracture-based patterning schemes.|
|The research was led by ICREA Professor and Group Leader Gustau Catalan, from the ICN2 Oxide Nanophysics Group. The first author of the article is Dr Kumara Cordero-Edwards, who is a former member of the Group and nowadays is developing her research at the UniversitÚ de GenÚve (Switzerland). The work counted with the participation of other researchers from the KTH-Royal Institute of Technology (Sweden) and ICREA Prof. Jordi Sort, from the Physics Department at the UAB.|
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