ABSTRACT
To get insight into the mechanisms involved in the creation of holes in thallium-based superconductors, the authors have carried out many systematic studies involving substitutions of various cations in crystal structure of thallium cuprate-based compounds and its implications on superconducting properties. This chapter discusses the results on the cation substitution studies in thallium compounds. It infers that double-rock-salt-layer in thallium compounds overlap with cuprate bands at the Fermi level. The chapter suggests that Incorporation of excess oxygen in thallium oxide layers, cation substitutions, or cation vacancies may play a role in terms of altering the number of charge carriers (holes) in the conduction band and hence superconducting properties.
