Elastic properties of SrTiO3 crystals at ultralow frequencies

The phase transition of SrTiO3 at 105 K has been examined by studying the t emperature dependence of the Young's modulus of SrTiO3 crystals along vario us directions. Dynamic Mechanical Analysis (DMA) at 10-140 K and 10-45 Hz h as been used for the experiments. The elastic behaviour is interpreted in t erms of Landau theory and the DMA results are compared with ultrasonic expe riments. The striking differences between the two types of data are attribu ted to the occurrence of domain wall motions at low frequencies. These moti ons are suppressed at high frequencies (ultrasonics). We have studied the t emperature behaviour of the low-frequency elastic constants of SrTiO3 as fu nction of external stress. The data analysis shows that the domain wall con tribution to the elastic constants is essentially suppressed with increasin g of uniaxial compression.