Thermoelectric properties of strained, lightly-doped La1–x­SrxCoO3 thin films

We report on the thermoelectric properties of strained, highly-oriented, lightly-doped La1–xSrxCoO3 thin films, grown on MgO (100) substrates by pulsed laser deposition. The large lattice mismatch (∼9%), along with the different thermal expansion coefficients, between La1–xSrxCoO3 and MgO, result in the incoherent growth of thin films and the generation of a tensile thermal strain (∼1%). Room temperature resistivity values of the films are similar to those of bulk samples, while the temperature dependence of resistivity of the films does not seem to be affected by the thermal strain. The Seebeck coefficient values of all investigated films are positive but lower than those of their bulk counterparts, throughout the measured temperature range. The lower values of the films' Seebeck coefficient are attributed to the stabilization of mixed Co spin state configuration, which is induced by the thermal strain. As a result of the reduced Seebeck coefficient values, the thermoelectric power factor is suppressed, ...