Electrical conductivity and crystal structure of pure and SrCO3-doped Na2CO3

The electrical conductivity of pure and SrCO₃-doped sodium carbonate has been measured in the temperature range 310–800 °C in air using a dc technique. Its concentration dependency is similar to that of the K₂CO₃–SrCO₃ system described recently (GUTH et al. 1986). The maximum conductivity could be observed at ≈ 20 mol.% SrCO₃. At temperatures > 440 °C, the conductivity of Na₂CO₃–SrCO₃ mixtures containing up to 80 mol.% SrCO₃ is larger than that of pure Na₂CO₃. X-ray investigations of slowly cooled samples show the mixtures to be heterogeneous. X-ray diffraction patterns of quenched mixtures containing 10 mol.% SrCO₃ show reflexes of a high temperature compound. SrCO₃, however, could not be detected. The lattice constants of this hexagonal compound Na₂Sr₄(CO₃)₅ which is isotyp with Na₂Ca₂Sr₂(CO₃)₅ described by CHEN and CHAO are a₀ = (1066.1 ± 0.4) pm and c₀ = (653.2 ± 0.2) pm.