Formation and Structural Characterization of 1:1 Ordered Perovskites in the Ba(Zn 1/3 Ta 2/3 )O 3 –BaZrO 3 System

The phase stabilities in the(1−x)Ba(Zn 1/3 Ta 2/3 )O 3 (BZT)‐xBaZrO 3 (BZ)system have been investigated using samples prepared by the mixed oxide method. The substitution of Zr 4+ destabilizes the 1:2 cation ordering in BZT and pro‐motes the formation of a cubic, 1:1 ordered structure with a doubled perovskite repeat. The homogeneity range of the 1:1 phase extends from x = 0.04 to approximately x = 0.25; substitutions beyond this range stabilize a disordered perovskite. The limits of stability of the 1:1 ordering coin‐cide with compositions previously found to exhibit anoma‐lies in their dielectric loss. The range of homogeneity is consistent with a “random layer” model for the 1:1 ordered “Ba{β′; 1/2 β 1/2 }O 3 ” structure. In this model the B× positions are assumed to be occupied exclusively by Ta 5+ , and the b× sites by a random distribution of Zn 2+ , Zr 4+ , and the remaining Ta 5+ cations. The validity of the model, where the ordered solid solutions can be represented by Ba{[Zn 2− y /3 Ta (1−2 y )/3 Zr y ] 1/2 [Ta] 1/2 }O 3 (y =2x)was con‐firmed by Rietveld refinements conducted using data col‐lected with a synchrotron X‐ray source.