title: Colossal negative thermal expansion in BiNiO3 induced by intermetallic charge transfer.
abstract: The unusual property of negative thermal expansion is of fundamental interest and may be used to fabricate composites with zero or other controlled thermal expansion values. Here we report that colossal negative thermal expansion (defined as linear expansion <-10(-4) K(-1) over a temperature range ~100 K) is accessible in perovskite oxides showing charge-transfer transitions. BiNiO(3) shows a 2.6% volume reduction under pressure due to a Bi/Ni charge transfer that is shifted to ambient pressure through lanthanum substitution for Bi. Changing proportions of coexisting low- and high-temperature phases leads to smooth volume shrinkage on heating. The crystallographic linear expansion coefficient for Bi(0.95)La(0.05)NiO(3) is -137×10(-6) K(-1) and a value of -82×10(-6) K(-1) is observed between 320 and 380 K from a dilatometric measurement on a ceramic pellet. Colossal negative thermal expansion materials operating at ambient conditions may also be accessible through metal-insulator transitions driven by other phenomena such as ferroelectric orders.
authors.affiliation: Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan. mazuma@msl.titech.ac.jp
authors.forename: Masaki
authors.initials: M
authors.lastname: Azuma
authors.forename: Wei-tin
authors.initials: WT
authors.lastname: Chen
authors.forename: Hayato
authors.initials: H
authors.lastname: Seki
authors.forename: Michal
authors.initials: M
authors.lastname: Czapski
authors.forename: Smirnova
authors.initials: S
authors.lastname: Olga
authors.forename: Kengo
authors.initials: K
authors.lastname: Oka
authors.forename: Masaichiro
authors.initials: M
authors.lastname: Mizumaki
authors.forename: Tetsu
authors.initials: T
authors.lastname: Watanuki
authors.forename: Naoki
authors.initials: N
authors.lastname: Ishimatsu
authors.forename: Naomi
authors.initials: N
authors.lastname: Kawamura
authors.forename: Shintaro
authors.initials: S
authors.lastname: Ishiwata
authors.forename: Matthew G
authors.initials: MG
authors.lastname: Tucker
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Shimakawa
authors.forename: J Paul
authors.initials: JP
authors.lastname: Attfield
mesh_terms: D001729:Bismuth / Q000737:chemistry*; D003461:Crystallography; D007811:Lanthanum / Q000737:chemistry; D008956:Models, Chemical; D008968:Molecular Conformation; D009532:Nickel / Q000737:chemistry*; D011312:Pressure; D013696:Temperature; D013816:Thermodynamics
chemical_list: D007811:Lanthanum; D009532:Nickel; C028007:nickel monoxide; D001729:Bismuth