The system Al2O3 and (Sr,Mg)-doped LaGaO3: phase composition and electrical properties

Mixtures of alpha-Al2O3 and La0.8Sr0.2Ga0.8Mg0.2O3-delta, with alpha-Al2O3 concentrations ranging from 1 to 20 wt.%, were uniaxially and isostatically pressed and finally sintered at 1500 degreesC for 4 h. The phase composition and microstructure were investigated by X-ray powder diffraction and scanning electron microscopy techniques. The electrical properties were studied by complex impedance spectroscopy in a wide range of temperatures (200-800 degreesC) in air. In the sintered bodies pure alpha-Al2O3 was not detected; the partial substitution of Al for Ga was suggested entailing the formation of the solid solutions of perovskite-type (La0.8Sr0.2)(Ga1-x-yAlxMgy)O3-delta and La0.8Sr0.2Ga1-xAlx O3-delta. alpha-Al2O3 added to La0.8Sr0.2Ga0.8Mg0.2O3-delta inhibited the grain growth of the majority phase. Under isothermal conditions, the electrical conductivity decreases with increasing alumina content, while the activation energies increase.