Low-frequency superelasticity and nonlinear elastic behavior of SrTiO3 crystals

To clarify the inconsistencies in existing elastic constant data of SrTiO3 in the vicinity of the 105 K phase transition we have studied the temperature dependence of the Young's modulus of SrTiO3 crystals. Dynamic mechanical analysis at 10-140 K and 10-45 Hz has been used for the experiments. We found two remarkable features: a giant elastic softening (superelasticity) below the cubic --> tetragonal phase transition, and elastic anomalies in the quantum paraelectric region between about 25 K and 45 K. The giant elastic softening is caused by domain-wall motion: it can he suppressed with uniaxial compression and does not occur in the [111] direction. Elastic anomalies observed in the quantum paraelectric region display nonlinear elastic behavior. We relate these nonlinear elastic anomalies with the appearance of polarization clusters. Our data can be consistently described assuming a freezing of the dynamical polar clusters below 25 K.