Lattice dynamics and phase transitions peculiarities of BaxSr1-xTiO3 solid solutions with high Sr content

In this study, the lattice dynamics and phase transition peculiarities of BaxSr1-xTiO3 solid solution samples with x = 1, 0.5 and 0.3 are investigated by the Raman spectroscopy in a wide temperature range. The compositional and temperature dependences of soft mode frequencies were obtained. In contrast to ceramics with x = 1 and 0.5, the soft E(TO) mode frequency in a solid solution with x = 0.3 exhibits temperature dependence similar to the classical behavior of the soft mode for displacement-type transitions. From the analysis of the activation energy of titanium ion jumps, it was found that with increasing strontium concentration, the mechanism of these jumps changes from thermal over the potential barrier to tunneling under the barrier. This, in turn, leads to a significant increase in the lifetime of the rhombohedral distorted state of the crystal lattice and suppression of the ferroelectric transition by the Slater mechanism.