Electrical conductivity and ionic transport number of Sr β-alumina single crystals prepared by a floating zone method

Sr β-alumina single crystals, Sr1−0.25xMg1−xAl10+xO17+0.25x (0 ≤ x ≤ 0.41) were prepared in the SrO-MgO-Al2O3 system by a floating zone method. The single crystals had a cleavage plane, which is parallel to (001) plane. The electrical conductivity parallel (σ) and perpendicular (σ⊥) to the cleavage plane had a maximum at x = 0.2. The σ was almost independent of oxygen partial pressure (PO2), while σ⊥ showed a PO2− 1/6 dependence in the low PO2 range (PO2 = 10− 4∼10− 13 Pa). The ionic transport numbers measured by a d.c. polarization method were almost unity in air at 1073 K to 1573 K.