Superelasticity in micro-scale shape memory ceramic particles

Shape memory ceramics that exhibit repeatable superelastic deformation are of considerable significance for possible energy damping and micro-actuation applications, and the present work aims to further establish the structural conditions required to avoid fracture in these brittle materials. Spray dried micro scale superelastic ceramic particles with a variety of grain structures were produced, ranging from single crystal to oligocrystal to polycrystalline particles. Micro-compression experiments showed that whereas polycrystalline samples fracture upon loading, oligocrystal and single crystal particles can exhibit cyclic superelasticity, the latter particles achieving highly reproducible superelasticity to over one hundred cycles with particle compressions up to 3.8% and dissipated energy up to 20-40 MJ/m(3) per cycle. The mechanisms of structural evolution and fatigue during cyclic loading are also explored. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.