Effect of Sintering Temperatures on the Crystal Structures of La0.9Sr0.1Ga0.8Mg0.2O3−δ

Abstract

The crystal structures of electrolyte materials of La0.9Sr0.1Ga0.8Mg0.2O3−δ (LSGM) for solid oxide fuel cells prepared by low- and high-temperature solid state reactions and laser rapid sintering are studied by structural refinements of XRD patterns. The results of structural refinements show that the three series of samples by low- and high-temperature solid state reactions and laser rapid sintering crystallized in different structures. They are identified to be cubic with space group Pm m 3 (denoted as C-LSGM), monoclinic with space group I2/a (denoted as M-LSGM) and orthorhombic with space group Imma (denoted as O-LSGM), respectively. To understand the effect of sintering temperatures on the crystal structures, the Gibbs free energies of three structures are calculated. It indicates that the cubic phase has the priority to form at relatively lower temperatures due to its lowest Gibbs energy while the formation of monoclinic and orthorhombic phases requires higher and highest sintering temperatures. This is in agreement with the experiment conditions of the preparation of the three series of samples.