Stress Induced Ferroelectric Phase Transitionin Quantum-Paraelectrics

The ferroelectric phase transition in some quantum-paraelectrics under the uniaxial stress is analyzed on the basis of the vibronically coupled two-band theory which takes into account the anharmonicity of lattice deformation. By calculating the electronic band structure and the density of states, it is shown that the uniaxial stress has an effect on the soft mode frequency similar to the one due to mixing in the case of mixtures of incipient ferroelectrics. Resultant critical stresses for the transition are consistent with available experimental data for KTaO 3 and SrTiO 3 .