Mechanical properties of sintered La9.33Si2Ge4O26 oxyapatite materials for SOFC electrolytes

Mechanical properties of La9.33Si2Ge4O26 prepared by mechanical alloying and subsequent sintering at 1300–1400 °C for 1 h were evaluated. Hardness and Young's modulus values in the range 7.3–9.6 GPa and 106–135 GPa, respectively, were obtained from nanohardness tests. The fracture toughness values derived from the Palmqvist method varied between 3.5 and 3.9 MPa m1/2 from classical microindentation test with an indentation load of 9.8 N. Yield stress (σy) was determined by inverse analysis from microhardness tests. The maximum value of σy (1829 MPa) was obtained for the sample sintered at 1400 °C showing the highest density (5.42 g/cm3).