Thermal expansion near the displacive phase transition in SrTiO3

The linear thermal expansion coefficients for monodomain crystals of SrTi${\mathrm{O}}_3$ have been measured near the displacive phase transition at 106.8 K. The results show marked shape, orientation, and history-dependent effects in the directions. In particular, these crystals do not have an isotopic thermal expansion coefficient above $T_c$. The thermal expansion results, in conjunction with other known properties of SrTi${\mathrm{O}}_3$, lead to a qualitative description in terms of the electret effect and raise questions as to the details of the critical dynamics near $T_c$.