CHARACTERIZATION, CONDUCTIVITY AND MECHANICAL-PROPERTIES OF THE OXYGEN-ION CONDUCTOR LA0.9SR0.1GA0.8MG0.2O3-X

The new oxygen-ion conductor La0.9Sr0.1Ga0.8Mg0.2O3-x has been prepare d by conventional solid-state reaction at high temperatures and charac terised by X-ray diffraction, scanning and transmission electron micro scopy, and conductivity (four-probe de and impedance)measurements. The room-temperature structure is orthorhombic, space group Pnma (no. 62) , with a = 5.5391(7) Angstrom, b = 7.8236(12) Angstrom, c = 5.5224(7) Angstrom. The material undergoes a phase transition at 445 K to a rhom bohedral structure. Mechanical property measurements at room temperatu re and at 1173 K give average strength measurements of 162 +/- 14 MPa and 55 +/- 11 MPa respectively. Conductivity and ionic transport numbe r measurements confirm predominantly ionic conduction. The contributio n from the grain boundary conductivity is extremely small at temperatu res below 673 K. At 1073 K, an ionic conductivity value of 0.12 S cm(- 1) was recorded in air.