Origin of the cubic-to-hexagonal phase transition in the Ba2NiWO6-BaTiO3 system

Microwave dielectric ceramics with the composition of (1-x)Ba(Ni
1/2
W
1/2
)O
3
-xBaTiO
3
(x = 0.1–0.5) were prepared by a solid-state reaction method. A cubic-to-hexagonal phase transition occurred from x = 0.15 to 0.5, where the cubic double perovskite structure transformed into the h-BaTiO
3
-type hexagonal perovskite structure. In this paper, we revealed a cluster model caused by a hopping mechanism as the origin of the cubic-to-hexagonal phase transition on the basis of the low frequency dielectric property results. This model was then proved by XRD analysis, XPS analysis, and HRTEM and EDS techniques, respectively.