Superior Perovskite Oxide‐Ion Conductor; Strontium‐ and Magnesium‐Doped LaGaO ₃ : II, ac Impedance Spectroscopy

Abstract

Alternating current impedance spectroscopy and electron microscopy were used to investigate the effect of grain boundaries in LSGM‐based materials. The impurity LaSrGa 3 O 7 existing in the samples La 0.8 Sr 0.2 Ga 1‐ y Mg y ‐O 3–0.5(0.2+ y ) ( y = 0.05–0.10) gives a contribution to a perfect or depressed grain‐boundary semicircle in the impedance spectroscopy. The depressed semicircle represents a constant phase element (CPE) indicating LaSrGa 3 O 7 is an oxide‐ion insulator. The grain‐boundary semicircle vanishes if a hydrogen‐containing atmosphere is applied. This fact may reflect proton conduction in LaSrGa 3 O 7 . In contrast, the impurity LaSrGaO 4 existing, for example, in the samples x = 0.20, y = 0.25–0.30 gives no grain‐boundary contribution to the impedance.