Nature of structural changes in LSM-YSZ nanocomposite material during thermal treatments

Abstract

Nanocomposite powders in the system (La1-xSx)(a)MnO3-YSZ((1-y)) [LSM-YSZ], as an attractive cathode material for high operating solid oxide fuel cell (SOFC), were obtained through ultrasonic spray pyrolysis (1.7 MHz) method. The principle of the synthesis is based on a single-step high temperature aerosol decomposition of atomized precursor solutions composed from yttria stabilized ZrO2 sol (average particle size similar to 60 nm) and corresponding aqueous nitrate and hydrogen peroxide solutions of La, Sr and Mn. Two starting systems were examined: (a) (La0.76Sr0.24)(0.93)MnO3 with 0% YSZ, and (b) (La0.77Sr0.23)(0.92)MnO3-YSZ(0.81) with corresponding molar ratio LSM/YSZ = 48:52. X-ray diffraction analysis of as-prepared powders showed the presence of a lanthanum magnesium oxide and yttrium zirconium oxide. Compositional homogeneity and particle morphology were determined by SEM analysis. LSM-YSZ obtained particles are spherical in shape, submicron in size and composed of primary subgrains. TEM analysis of ultra-cross section revealed dense-packed nanosized grains, several tens of nanometers in diameter. After powders calcination TEM observations confirmed dense particle structure composed of primary grains, with a mean diameter of around 100 nm. The structural changes expressed through the crystallite growth were analyzed by nonisothermal differential scanning calorimetry (DSC).