Enhanced dielectric and tunable performance in BCZT91/BCZT87 bilayer ceramics

The BCZT91/BCZT87 bilayer ceramics are prepared via solid-state reaction method to investigate the dielectric and tunable performance. The results indicate that the permittivity of bilayer ceramics is larger than that of monolayer ceramics due to the influence of space charge effect existing at interface. Meanwhile, a model evolving from the series equivalent circuit model and Landau-Devonshire theory is used to study the tunability of bilayer ceramics. The results indicate that the tunability of bilayer ceramics is obviously improved from-29% to-39% at --400kV/m due to the influence of space charge effect when the thickness ratio of BCZT91 layer is 0.67. The similar result is also obtained when the thickness ratio is 0.50. The enhanced tunability accompanying with low loss tangent makes the figure of merit of bilayer ceramics precede monolayer ceramics. The results indicate that it is an effective method to improve the tunable performance of ceramics by introducing bilayer structure.