Cation Ordering Transformations in the Ba(Zn1/3Nb2/3)O3‐La(Zn2/3Nb1/3)O3 System

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Abstract
Single‐phase perovskites were formed in the (1−x)Ba(Zn1/3Nb2/3)O3‐(x)La(Zn2/3Nb1/3)O3 system for compositions with 0.0≤x≤0.6. Although the stability of the trigonal “1:2” ordered structure of the Ba(Zn1/3Nb2/3)O3 end member is very limited (0.0≤x≤0.05), low levels of lanthanum induce a transformation to a cubic, “1:1” ordered structure that has a broad range of homogeneity (0.05≤x≤0.6). Samples with x > 0.6 were comprised of La3NbO7, ZnO, and a perovskite with x = 0.6. The cubic 1:1 phases were fully ordered and no evidence was found for a compositionally segregated microstructure. These observations could not be reconciled in terms of a “space‐charge” model; rather, they supported a charge‐balanced, “random‐site” structure for the 1:1 cation‐ordered Ba(β1/2′β1/2″)O3 phases.