A related structure with the general formula
Bi2RE2Co1.7–2Ox (RE = Ca or Sr), which contains an expansion
of the rock salt layer present in Co3O4O9, can form .23,74
Although the superlattice structure does lead to relatively
low thermal conductivities of ∼0.8 and ∼1.2 W K−1 m−1 for
Bi2Ca2Co1.7Ox
73 and Bi2Sr1.94La0.06Co2O9,
74 respectively,