Atomic resolution transmission electron microscopy of the microstructure of ordered Ba(Cd _1/3Ta _2/3)O ₃ perovskite ceramics

Microstructures of ordered Ba(Cd _1/3Ta _2/3)O ₃ perovskite dielectric ceramics with and without a boron additive have been observed by atomic resolution transmission electron microscopy (TEM). The selected area electron diffraction and lattice image show a well-ordered structure with hexagonal symmetry (lattice constants of a∼5.8 Å and c∼7.1 Å) in the ordered Ba(Cd _1/3Ta _2/3)O ₃ with a boron additive, which is similar to those in ordered Ba(Zn _1/3Ta _2/3)O ₃ and Ba(Mg _1/3Ta _2/3)O ₃ ceramics. Ordered domains with a twin crystallographic relationship and high-density domain interfaces induced by ordering were observed in the ordered Ba(Cd _1/3Ta _2/3)O ₃ without a boron additive sintered at a relatively high temperature. Atomic resolution TEM further revealed the conservative twin boundaries along (001) and (110) planes and non-conservative antiphase boundaries with a projected displacement vector of the type [001] in the ordered Ba(Cd _1/3Ta _2/3)O ₃ without a boron additive. Finally, the energetics of different domain interfaces are discussed with the interfacial structures in ordered Ba(Cd _1/3Ta _2/3)O ₃ ceramics revealed by an electron microscope.