Soft mode behavior and phase transition in BaxSr1-xTiO3 -: art. no. 252906

We present a clear picture for soft mode behavior and ferroelectric phase transition in BaxSr1-xTiO3 throughout the concentration range (x from 0 to 1), by proposing a simple way to quantitatively explain all the experimental data in the literature. The approach was realized through combining the transverse-field Ising model with the Lyddane-Sachs-Tell relation, cell volume effect, and ferroelectric distortion. It is found that, with the increase of impurity concentration, the soft mode softens in the paraelectric phase, and stiffens in the ferroelectric one, where the phase transition will change from the second order to the first order at high concentration (x >= 0.57). We have further shown the quantum effect on the soft mode in BaxSr1-xTiO3 with the concentration below 0.10. (c) 2005 American Institute of Physics.