EFFECTS OF OXYGEN NONSTOICHIOMETRY AND CATIONIC SUBSTITUTIONS ON THE PROPERTIES OF SR2RUO4+DELTA

A systematic study of polycrystalline Sr2RuO4+delta has been carried o ut by varying its oxygen stoichiometry. The oxygen-annealed sample wit h excess oxygen (delta = 0.25) exhibits pronounced semiconducting beha viour while the argon-annealed phase without excess oxygen (delta = 0) exhibits degenerate semiconducting behaviour. The conduction mechanis m is analysed. The air- and oxygen-annealed phases obey a variable-ran ge hopping (VRH) mechanism. Substitution at the Sr site for the first time by Ca, Ba and La and at the Ru site by Ti, Mn, Li and Pb has been carried out and the resulting properties are studied. Among these sub stitutions La substitution lowers resistivity and the sample behaves l ike argon-annealed Sr2RuO4. All other substitutions make Sr2RuO4+delta more semiconducting. (C) 1998 Elsevier Science S.A. All rights reserv ed.