Dielectric and pyroelectric properties of BaxSr1-xTiO3:: Quantum effect and phase transition

We have carried out a detailed investigation on the dielectric and pyroelectric properties in BaxSr1-xTiO3 (BST) throughout the concentration range (x from 0 to 1), with the emphasis on quantum effect and phase transition. The approach was realized by employing the transverse-field Ising model, taking into account the cell volume effect and ferroelectric distortion, to quantitatively explain most of the experimental observation in the literature. Together with the nonzero-field scaling analysis, we have presented a clear picture for the quantum effect in BST with small impurity concentrations and at low temperatures through electric field dependence of the dielectric and pyroelectric characteristics. It is found that, with the increase of concentration, the BST system undergoes the variation from the quantum paraelectric, to quantum ferroelectric, and to classical ferroelectric with the second-order phase transition evolving into the first-order one at concentrations higher than 0.57.