Thermal Properties Of Sr-doped LaMnO₃ Superlattice

Fuel cells power generation technology for its high efficiency, low emissions, light weight, non-polluting, fuel diversification of fuel, etc., has been successfully applied to the spacecraft and progressively developed to ground application. As an important component of the system of fuel cell, matched thermal expansion is very important. At the temperature which range from room temperature to manufacture temperature, the cathode materials should match with the coefficient of thermal expansion the other element in groups, so as to avoid crack, deformation and loss. The cathode material of solid oxide fuel cells (SOFC) is Sr-doped LaMnO₃, because the coefficient of thermal expansion of pure LaMnO₃ is slightly lower than the coefficient of thermal expansion of the electrolyte, so we can increase the coefficient of thermal expansion of the cathode material by Sr doped in LaMnO₃, so that the cathode materials and electrolytes have better matches. But the researchs on the thermal expansion, etc. thermal properties about La_1-xSr_xMnO₃ are not many, and so the studies of the thermal properties have an important guiding role for the research and manufacturing of the cathode materials.Classical atomistic simulations based on lattice dynamics theory and Born core-shell model were performed to systematically study the crystal structure and thermal properties of La_1-xSr_xMnO₃ superlattice. We calculate thermal properties such as the coefficient of thermal expansion, phonon density of states, specific heat, and Debye temperature at different temperatures and for different Sr-doping concentrations. It is found that the lattice constants b and c of superlattice increases, but a reduces as the temperature increases. Both the specific heat of constant volume and the coefficient of thermal expansion of La_1-xSr_xMnO₃ superlattice reduce with the increasing of Sr-doping concentrations. Debye temperature of La_1-xSr_xMnO₃ superlattice increases from about 630 K to 800 K when Sr-doping concentration increases from 0 to 3/4. Some simulation results correspond with experimental data, and we anticipate our results will be helpful to select the base on which La_1-xSr_xMnO₃ materials are prepared.