Crystal defects induced by evaporation of Co and Zn on the structure and microwave properties of Ba(Co0.7Zn0.3)1/3Nb2/3O3 ceramics

Abstract

There is no significant difference in grain size, B-site 1:2 ordering degree and domain structure of Ba(Co0.7Zn0.3)1/3Nb2/3O3 (BCZN) ceramics annealed at 1300 °C–1350 °C for 30 h. In contrast, the Q × f values of BCZN ceramics annealed at 1350 °C for 30 h decreases sharply to 53,900 GHz (at 7 GHz) from ~84,700 GHz for its counterpart annealed at 1300 °C for 30 h. EPMA results show that the deficiency of zinc and cobalt appears in the BCZN ceramics. Co and Zn loss in BCZN ceramics leads to the formation of crystal defects that have a significant influence on electrical properties and dielectric loss. With the increasing annealing temperature, the resistivity and activation energy Ea of as-annealed BCZN ceramics decrease, indicating higher crystal defect density in ceramics. The crystal defects rather than B-site 1:2 ordering play a dominant role in determining the dielectric loss of BCZN ceramics containing evaporative Zn and Co.