On the use of photoacoustic technique for monitoring the thermal properties of lanthanum strontium cobalt ferrite-yttria stabilized zirconia two-layer systems

In this work, lanthanum strontium cobalt ferrite (La0.6Sr0.4Co0.2Fe0.8O3 − δ) films deposited by spray-pyrolysis onto commercial yttria stabilized zirconia substrates were investigated by photothermal spectroscopy. It is shown that by using the thermal-electrical analogy model it is possible to obtain the thermal properties of two-layer composite systems simultaneously, without the need to spread them, and thus to evaluate the thermal mismatch between the substrate and the deposited film. The thermal diffusivity of the 8YSZ substrate was found to be 6.6 × 10−3 cm2s−1, whereas for the La0.6Sr0.4Co0.2Fe0.8O3 − δ films it ranged between 0.47 and 9.26 × 10−4 cm2s−1. We have found that for film thickness beyond 3.06 μm the thermal expansion coefficient becomes relevant, indicating that the optimum film deposition time lies between 10 and 20 min.