Raman study of high temperature insulator-insulator transition in Ba2Co9O14

Abstract The insulator-insulator transition, at T t  = 570 K, in layered cobalt oxide Ba 2 Co 9 O 14 was investigated using Raman scattering technique. High temperature (300–800 K) measurements have evidenced no structural transition occurring at T t . The obtained results are rather consistent with low to high spin-state transition of Co 3+ ions in the Co 3 O 12 octahedral trimer. More precisely, only one cobalt ion located in the central octahedron of the trimer undergoes this transition.