Thermal behaviour of La 0.8Sr 0.2Fe 1− xGa xO 3− δ ( x = 0 or x = 0.3)

Abstract

The thermo-mechanical behaviours of La 0.8Sr 0.2Fe 1− x Ga x O 3− δ ( x = 0 or x = 0.3) ceramics for catalytic membrane reactors are studied up to 1100 °C under air and nitrogen atmospheres. XRD data, thermogravimetric and dilatometric analyses associated with Young's modulus measurements give a better understanding and a qualitative description of the mechanical behaviour of the perovskite materials as a function of temperature. First, a decrease of Young's modulus from room temperature to 300–400 °C is attributed to FeO 6 octahedrons distorsions of the monoclinic (or orthorhombic) phase. After phase transition, the rhombohedral phase exhibits a higher TEC and a stiffening of the perovskite structure probably due to less distorted FeO 6 octahedrons. Finally, at higher temperatures ( T > 800 °C), thermogravimetric data show a weight loss attributed to oxygen departure from the perovskite structure leading to a large cell expansion. This study presents the structural evolution of both materials and its impact on the thermal and mechanical behaviours that have to be considered for industrial uses.