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 pyroelectric properties of polydomain epitaxial Ba0.6Sr0.4TiO3 thin films. Polydomain a1/a2/a1/a2, ca1/ca2/ca1/ca2, aa1/aa2/aa1/aa2, r1/r2/r1/r2 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 a1/a2/a1/a2-PE and ca1/ca2/ca1/ca2-c, c-PE, respectively, in which the pyroelectric coefficients |pi| are larger than 0.6 μC/cm2 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. •The phase structures and physical properties of polydomain epitaxial BaSr0.6Ti0.4O3 thin films have been investigate based on Landau–Devonshire thermodynamic theory.•Polydomain a1/a2/a1/a2, ca1/ca2/ca1/ca2, aa1/aa2/aa1/aa2, r1/r2/r1/r2 phases and single domain c, PE phases have been found in the misfit strain-temperature phase diagram.•A distinguished in-plane and out-of-plane pyroelectric response appears near the phase boundaries of a1/a2/a1/a2-PE and ca1/ca2/ca1/ca2-c, c-PE, respectively, in which the pyroelectric coefficients |pi| are larger than 0.6 μC/cm2 K.