Electrical conductivity of non-stoichiometric Sr β-alumina single crystals prepared by a floating zone method

Non-stoichiometric Sr β-alumina single crystals were prepared in SrO–MgO–Al2O3 system by a floating zone (FZ) method. The range of non-stoichiometry was determined as Sr1−0.25xMg1−xAl10+xO17+0.25x, where 0<x≤0.41. The lattice parameters of a increased and c decreased with increasing SrO content in the solid solution range. The single crystals had a cleavage plane parallel to the (001) plane and growth direction. The electrical conductivity parallel and perpendicular to the cleavage plane showed maximum at x=0.2 (i.e., 13.8 mol% SrO). The activation energy of electrical conductivity parallel to the cleavage plane (140 to 165 kJ/mol) was almost the same as that perpendicular to the cleavage plane (150 to 170 kJ/mol).