| 초록 |
The perovskite solid solutions of the $Sr_{1-x}Mg_xFe{^{3+}}_{1-{ tau}}Fe{^{4+}}_{ tau}O_{3-y}$ system (x=0.0, 0.1, 0.2, and 0.3) were synthesized in $N_2$ at $1,150^{ circ}C$ . X-ray powder diffraction study assured that all the four samples had cubic symmetries(SM-0: $3.865{ AA}$ , SM-1: $3.849{ AA}$ , SM-2: $3.833{ AA}$ , and SM-3: $3.820{ AA}$ ) and that the lattice volumes decreased steadily from $57.7{ AA}^3$ to $55.7{ AA}^3$ with x values. The nonstoichiometric chemical formulas were determined by Mohr salt analysis and with the increase of x values the amounts of $Fe^{4+}$ ion and oxygen were decreased simultaneously. Thermal analysis showed that SM-0 started to lose its oxygen at $450^{ circ}C$ and SM-1, Sm-2, and SM-3 began to lose their oxygen at around $350{ sim}400^{ circ}C$ . SM-0 showed almost reversible weight change in the cooling process. All the samples exhibited semiconducting behaviors in the temperature range of $10{ sim}400^{ circ}C$ . Conductivities of the 4 samples were decreased in the order of SM-0, SM-1, SM-2, and SM-3 at constant temperature. The activation energies of the conductions were in the range of 0.176 eV~0.244 eV. |
