Effect of strontium ion doping on structural, thermal, morphological and electrical properties of a co-doped lanthanum manganite system

Abstract

An effect of strontium ion doping on the structural, thermal, morphological and electrical properties of a co-doped lanthanum manganite system, La1−xSrx Mn0.85Fe0.05Co0.05Ni0.05O3+i (x = 0-0.4 mole) is inves- tigated for the solid oxide fuel cell cathode application. The submicron and rhombohedral structured sample, synthesized by the Pechini method, exhibited a decrease in the unit cell volume with increasing x. The thermogravimetry study portrayed nearly fivefold weight loss for a sample with x = 0.3 mole rela- tive to the La0.75Sr0.25MnO3+i and suggested an improvement in the concentration of the oxygen vacancy for ion migration due to the co-doping effect. It also showed sufficiently high electrical conductivity (∼ 76 Sc m−1 )a t 650◦C along with a low activation energy (∼0.15 eV), a comparable coefficient of thermal expansion (∼12.1 × 10 −6 ◦ C −1 ) and a chemical compatibility with the solid electrolytes. The results were The Pechini method (15) was applied to prepare the LSMFCN. Strontium acetate hydrate (97%), lanthanum (III) acetate hydrate (99.9%), manganese (II) acetate tetrahydrate (99%), iron (II) acetate (95%), cobalt (II) acetate tetrahydrate (99%) and nickel (II) acetate tetrahydrate (99%), all from the Aldrich or Fluka Chemicals (USA), were dissolved in distilled water under stirring in an order to obtain a clear 0.3 M solution (50 ml). Ethylene glycol (99%, Aldrich; an esterification agent) and then cit- ric acid (99.5%, Aldrich; a chelating agent), both with mass equals to the total mass of cations available, were added dropwise under stirring. The continuous stirring of solution at ∼80 ◦