Plasticity and an Inverse Brittle-to-Ductile Transition in Strontium Titanate

The use of ceramic materials is often restricted by a transition from ductile behavior to brittle fracture with decreasing temperature. For example, strontium titanate ( ${\mathrm{SrTiO}}_3$) is known to be extremely fragile and brittle below $1300\mathrm{K}$. It is therefore surprising to find that ${\mathrm{SrTiO}}_3$ single crystals can be deformed in compression below $1050\mathrm{K}$ again. Extensive plastic deformation up to $7\%$ strain at low yield stresses of the order of only $120\mathrm{MPa}$ is possible at room temperature. Low temperature plasticity is carried by the same $〈110〉\{1\overline{1}0\}$ dislocations as the high temperature deformation along the $〈001〉$ axis. From this we conclude that these dislocations must exist in two different core configurations.