Mechanical behavior of La0.8Sr0.2Ga0.8Mg0.2O3 perovskites

This paper examines the important mechanical properties of commercially purchased La0.8Sr0.2Ga0.8Mg0.2O3 at room temperature and 800 degrees C. Sr and Mg-doped lanthanum gallates (LSGM) are strong candidates for use as solid electrolytes in lower temperature solid oxide fuel cells operating at or below 800 degrees C. The material was found to be phase pure with a Young's modulus value of similar to 175 GPa. The four point bending strength of the LSGM samples remained almost constant from 121 +/- 35 MPa at room temperature to 126 +/- 20 MPa at 800 degrees C. The fracture toughness, as measured by the single edge V notch beam (SEVNB) method, was 1.22 +/- 0.06 MPa root m at room temperature, 1.04 +/- 0.09 MPa root m at 700 degrees C followed by a small increase 1.31 +/- 0.16 MPa root m at 800 degrees C. We also report, for the first time, the static subcritical (or slow) crack-growth (SCG) behavior of natural cracks in LSGM performed in four point bending tests at room temperature. The exponent of a power-law representation in the SCG tests was found to be n = 15, a rather low value showing LSGM to be highly susceptible to room temperature SCG. (C) 2008 Elsevier Ltd and Techna Group S.r.l. All rights reserved.