A study of superlattice ordering in substituted bismuth oxides is proposed. Bismuth rich compositions at the 14:1 B:M (where M = W/La and Ta) ratio will be investigated. These systems show very high ionic conductivity at elevated temperature, but there is evidence of superlattice ordering at lower temperatures, which dramatically lowers conductivity. This proposal seeks to clarify the superlattice ordering in these systems with a view to correlating the observed conductivity behaviour with changes in cation and vacancy/ordering.