Unique features of strontium titanate

Some novel features of strontium titanate are presented. First, it reveals secondary ferroicity when exposed to an external electric field in its tetragonal paraelectric state. It is shown on isotopically doped (SrTiO3)-O-18 (STO18) that odd-oriented ferroelastic domains can be switched under anomalously large electrostriction such as to create a perfect axially orientated state. Second, the strong non-linear dielectric response of STO18 can be described within the frame of a classic equation of state involving a nonlinearity coefficient with non-classic temperature dependence after correction for a contribution to random-field induced polar nanoregions. Third, static nonzero-external field scaling analysis reveals a non-classic exponent a = delta/(delta - 1) = 1.62 when respecting the validity of the quantum temperature concept in the vicinity of T-c approximate to 25 K. Fourth, polarized microscopy confirms that the isotope-induced ferroelectric low temperature phase is probably triclinic rather than orthorhombic. This results from a competition between the terragonal antiferrodistortive and a rhornbohedral,ferroelectric lattice distortion.