Influence of phase transformations on mechanical properties of novel ceramics for solid oxide fuel cell anode applications

Mechanical properties and phase stability of reoxidation-stable anode materials are reported. Elastic moduli of Sr0.895Y0.07TiO3−δ and La0.20Sr0.25Ca0.45TiO3 are characterized from room temperature up to typical operation temperatures. Anomalies in the elastic moduli are followed by X-ray diffraction investigations. The SYT crystal structure is confirmed to change reversibly from pseudo-tetragonal to cubic symmetry at ~200 °C under reducing conditions, leading to a local maximum in the elastic modulus at ~270 °C. The phase transition temperature decreases for SYT exposed to air. The elastic modulus of LSCT reveals two local minima at ~310 °C and ~740 °C. The XRD study confirms pseudo-tetragonal 1→ pseudo-tetragonal 2→ cubic transition sequence at ~300 °C and ~700 °C, respectively, with an anomalous reverse of the crystal lattice parameters during the pseudo-tetragonal 1→ pseudo-tetragonal 2 transition.