Local structure analysis of Nb-related perovskite materials

Yoneda, Yasuhiro   ; Kohara, Shinji*; Nagata, Hajime*; Fu, D.*; Takenaka, Tadashi*

NaNbO, KNbO, and AgNbO have rhombohedral structure at low temperatures. The phase transition depends on -site ion with NbO octahedron. NaNbO and KNbO have structural phase transition from rhombohedral to orthorhombic with increasing temperature. On the other hand, the phase transition of AgNbO occurs from rhombohedral to monoclinic. Since the rhombohedral structure is a highly ordered average structure, it tends to be subject to the influence of local randomness. We performed local structure analysis by using atomic pair-distribution function (PDF). The Nb-O bond clearly appeared in the observed distribution for NaNbO, but degraded in that for AgNbO. The difference of local structures causes different successive phase transitions for the Nb-related perovskite materials.