Unusual Thermal Expansion in Gd_1-XS_XrMnO₃ System

抄録

Gd_1-xSr_xMnO₃ has been studied as the cathode material for solid oxide fuel cells (SOFC).Gd_1-xSr_xMnO₃ with perovskite structure was found to have negative thermal expansion. The measurements of XRD, thermal expansion, TG-DTA and high temperature XRD were performed for this system. The crystal structure for 0.0≦X≦0.4 is orthorhombic and for X=5, tetragonal. The unusual thermal expansion is observed within 0.0≦X≦0.2, while the composition with X≧0.3 shows normal behavior. TG-DTA and high temperature XRD measurements show no phase transition and no release of oxygen atom. Curiously the cell volume increases with increasing temperature, however, a-axis decrease in the region of 0.0≦X≦0.2. This may be due to the unusual thermal expansion.