Thermo-Optical Study of Short-Range Polar Order in a Ferroelectric Phase: The Ca2+ Impurity-Induced Ferroelectric Phase in SrTiO3
The magnitudes and temperature dependences of the root-mean-square of polarization fluctuations, which characterizes short-range ordering below TC, are determined for the first time for Sr0.986Ca0.014TiO3 single crystals, using temperature measurements of light refraction made in a manner developed by the authors. Ab initio calculations of the equilibrium structures and total energies of three lowtemperature phases for SrTiO3 and CaTiO3 are performed and the symmetry of the ground state of their solid solution is identified on the basis of the obtained results. Features of short- and long-range ordering in the Ca2+-induced ferroelectric phase of the Sr1 − xCaxTiO3 system are discussed.