Effects of rock-salt layer on electronic and oxide ionic mixed conductivity in strontium titanate, SrO(SrTiO3)n (n = 1, 2, ∞)

Electronic conductivity and oxygen permeation properties of analogous compounds of SrO(SrTiO₃)_n (n = 1, 2) and SrTiO₃ were investigated. Electronic conductivity and oxide ion conductivity decrease with increasing n, and SrTiO₃ shows much higher conductivity. The effects of Co doping on oxide ion conductivity and electronic conductivity were also examined and it is observed that it is effective for increasing electrical conductivity and the oxygen permeation rate. Hall effect measurements suggests that the low electron-hole conductivity in Co-doped SrO(SrTiO₃)_n (n = 1, 2) can be assigned to a low mobility, which may result from the low electron and atomic density in the Sr-O rock-salt layer. Quantum mechanical calculations of the electron density also indicate low electron density in the rock-salt layer. This study reveals that the rock-salt layer consisting of Sr-O disturbs electron transfer in SrTiO_X oxide and that the perovskite layer has much higher electronic and oxide ionic conductivity.