Structure and Dielectric Properties of the Ba(Mg1/3Nb2/3)O3‐La(Mg2/3Nb1/3)O3 System

A complete range of perovskite solid solutions can be formed in the (1 − x )Ba(Mg 1/3 Nb 2/3 )O 3 ‐ x La(Mg 2/3 Nb 1/3 )O 3 (BMN‐LMN) pseudobinary system. While pure BMN adopts a 1:2 cation ordered structure, 1:1 ordered phases are stabilized for 0.05 ≤ x ≤ 1.0. Dark‐field TEM images indicate that the La‐doped solid solutions are comprised of large 1:1 ordered domains and no evidence was found for a phase‐separated structure. This observation coupled with the systematic variations in the intensities of the supercell reflections supports a charge‐balanced “random‐site” model for the 1:1 ordering. The substitution of La also induces a transformation from a negative to positive temperature coefficient of capacitance in the region 0.25 ≤ x ≤ 0.5.