Phase diagram and pyroelectric response of polydomain epitaxial Ba0.6Sr0.4TiO3 thin films

A nonlinear thermodynamic theory is used to investigate the phase structures, polarization and pyroelec-tric properties of polydomain epitaxial Ba0.6Sr0.4TiO3 thin films. Polydomain a(1)/a(2)/a(1)/a(2), ca(1)/ca(2)/ca(1)/ca(2), aa(1)/aa(2)/aa(1)/aa(2), r(1)/r(2)/r(1)/r(2) phases and single domain tetragonal c, paraelectric PE phases have been found in the misfit strain-temperature phase diagram. Note that the polydomain phases are found to be more complicated than single domain phases, which also leads to the variability of pyroelectric properties. The results of pyroelectric coefficients reveal that a distinguished in-plane and out-of-plane pyroelectric response appears near the phase boundaries of a(1)/a(2)/a(1)/a(2)-PE and ca(1)/ca(2)/ca(1)/ca(2)-c, c-PE, respectively, in which the pyroelectric coefficients vertical bar p(i)vertical bar are larger than 0.6 mu C/cm(2) K, exceeding most experimental and theoretical values. It is found that the maximum in-plane and out-of-plane pyroelectric coefficients occur under the strain of 0.23% and -0.225% at room temperature, respectively. The giant pyroelectric performance of polydomain Ba0.6Sr0.4TiO3 thin films may provide potential to highly sensitive infrared detectors.y