Characterisation, conductivity and mechanical properties of the oxygen-ion conductor La0.9Sr0.1Ga0.8 Mg0.2O3−x

Abstract

The new oxygen-ion conductor La _0.9 Sr _0.1 Ga _0.8 Mg _0.2 O _3-x has been prepared by conventional solid-state reaction at high temperatures and characterised by X-ray diffraction, scanning and transmission electron microscopy, and conductivity (four-probe dc and impedance) measurements. The room-temperature structure is orthorhombic, space groupPnma (no. 62), with a=5.5391(7) Å, b=7.8236(12) Å, c=5.5224(7) Å. The material undergoes a phase transition at 445 K to a rhombohedral structure. Mechanical property measurements at room temperature and at 1173 K give average strength measurements of 162±14 MPa and 55±11 MPa respectively. Conductivity and ionic transport number measurements confirm predominantly ionic conduction. The contribution from the grain boundary conductivity is extremely small at temperatures below 673 K. At 1073 K, an ionic conductivity value of 0.12 S cm ^-1 was recorded in air.