title: Synthesis and physical properties of layered Ba(x)CoO₂.
abstract: A layered cobaltite Ba(x)CoO2 (x = 0.19, 0.28, 0.30, 0.33) was synthesized by an ion exchange technique from the layered Na(x)CoO2 precursors. The phase composition and physical properties were investigated. Ba(x)CoO2 is isomorphic to the precursor Na(x)CoO2. The magnetic susceptibility of Ba(x)CoO2 decreases with increasing barium content and shows a Curie-Weiss-like behavior at temperatures above 50 K. The resistivity is sensitive to the barium content. As the barium content increases from 0.19 to 0.33, a crossover from a semiconducting behavior to a metallic behavior was observed. The Seebeck coefficient of Ba(x)CoO2 is insensitive to the barium content due to the tradeoff effect between the carrier concentration and the Co(4+) content, while the thermal conductivity increases with the increasing barium content from 0.19 to 0.33 owing to the ordered state of Ba ions between the CoO2 layers.
authors.affiliation: Key Laboratory of Transparent Opto-Functional Advanced Inorganic Materials, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050, P. R. China.
authors.forename: Jinfeng
authors.initials: J
authors.lastname: Liu
authors.forename: Xiangyang
authors.initials: X
authors.lastname: Huang
authors.forename: Danfeng
authors.initials: D
authors.lastname: Yang
authors.forename: Guisheng
authors.initials: G
authors.lastname: Xu
authors.forename: Lidong
authors.initials: L
authors.lastname: Chen