Elastic Anomaly and Internal Friction of Ba0.5Sr0.5Co0.8Fe0.2O3 and La0.58Sr0.4Co0.2Fe0.8O3

Elastic modulus and internal friction of Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCF) and La0.58Sr0.4Co0.2 Fe0.8O3-delta (LSCF) were determined from resonance frequencies and damping behavior, respectively, using an impulse excitation method. An elastic anomaly for BSCF around 476 K, with a corresponding peak in the internal friction, is attributed to the experimentally confirmed spin transition of Co3+. LSCF is in a ferromagnetic state below similar to 220 K and in a paramagnetic state above similar to 250 K. The elastic modulus of LSCF exhibits an anomaly between 473 and 1113 K, which is attributed to a transition from rhombohedral to cubic symmetry

Thermo-mechanical properties of La(2)NiO(4+delta)

Elastic and fracture behavior of La2NiO4+delta have been assessed. Fracture stress and elastic modulus of porous La2NiO4+delta were evaluated from room temperature (RT) up to 900 A degrees C on the basis of 4-point bending tests. Both parameters increase slightly from RT to 700 A degrees C. However, at higher temperatures the elastic modulus decreases, whereas the fracture stress increases. In addition, elastic modulus and damping/internal friction of dense specimens were measured by a resonance method. A strong change of elastic modulus and internal friction between RT and 100 A degrees C appears to be related to an orthorhombic-tetragonal phase transition. No indications of phase transition can be observed at higher temperatures. Although thermogravimetric measurements suggest that oxygen was continuously released from the lattice up to 1000 A degrees C with increasing temperature, the thermal expansion coefficient showed a rather stable value from RT up to 1000 A degrees C