Ferro-Elasticity in Rhombohedral Crystals of Sc-Stabilized ZrO₂

Ten mol% Sc-stabilized zirconia (10ScSZ) is a solid electrolyte used in high-temperature electrochemical devices such as solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs). This study investigated its mechanical properties under heating, revealing ferro-elastic behavior using dynamic mechanical analysis (DMA) and uniaxial compression tests. DMA analysis revealed that the storage modulus decreases up to the phase transition temperature of 590°C, reaching a minimum at this temperature, and then increases at higher temperatures. The peak of temperature-dependent internal friction showed frequency dependence below the transition temperature, with activation energies calculated to be 6.5 and 5.7 eV for measurement at 2.5 and 4.0 N, respectively. Stress-strain curves at 200 and 300°C showed non-linear behavior, with changes in slope and residual strain. Domain switching, confirmed by scanning electron microscopy observation, supports the presence of ferro-elasticity in 10ScSZ. This ferro-elastic behavior may enhance the toughness of SOFCs, SOECs, and other high-temperature devices. Furthermore, the observation of ferro-elasticity in the rhombohedral ScSZ suggests that the mechanical properties of ScSZ, including those with additives like Ce, may depend on thermal history due to phase ratio changes. This highlights the importance of thermal history for the mechanical properties in thermally-cycled devices.