Electrical conductivity and crystal structure of pure and SrCO 3 ‐doped Na 2 CO 3

The electrical conductivity of pure and SrCO 3 ‐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 K 2 CO 3 –SrCO 3 system described recently (GUTH et al. 1986). The maximum conductivity could be observed at ≈ 20 mol.% SrCO 3 . At temperatures > 440 °C, the conductivity of Na 2 CO 3 –SrCO 3 mixtures containing up to 80 mol.% SrCO 3 is larger than that of pure Na 2 CO 3 . X‐ray investigations of slowly cooled samples show the mixtures to be heterogeneous. X‐ray diffraction patterns of quenched mixtures containing 10 mol.% SrCO 3 show reflexes of a high temperature compound. SrCO 3 , however, could not be detected. The lattice constants of this hexagonal compound Na 2 Sr 4 (CO 3 ) 5 which is isotyp with Na 2 Ca 2 Sr 2 (CO 3 ) 5 described by CHEN and CHAO are a 0 = (1066.1 ± 0.4) pm and c 0 = (653.2 ± 0.2) pm.