Phase transition and local structure analysis of NaNbO

Yoneda, Yasuhiro   ; Kobune, Masafumi*; Wada, Satoshi*; Fu, D.*

NaNbO shows a complex phase transition sequence. The average structure transformed from an orthorhombic to rhombohedral structure at the phase transition temperature. This phase transition has been found to be diffuse and the orthorhombic and rhombohedral phases coexist at wide temperature ranges. The origin of the diffuse phase transition should be the randomness of the local structure. We performed atomic-pair distribution function analysis by using NaNbO samples grown by various synthesis method to clarify the relationship between the local structure and the phase transition. We demonstrated that the off-center shift of Nb atoms from the center on NbO ocrahedra coupled with the rhombohedral to orthorhombic phase transition.