Tailored wide-frequency dielectric behavior of polyimide composite films with BaxSr1-xTiO3 perovskites ceramic particles

A series of BaxSr1-xTiO3 (x=0.2, 0.4 and 0.6, BST) ferroelectric ceramics were prepared by conventional solid state reaction method. Crystal structure, surface morphology and dielectric properties of the BST ceramics and polyimide (PI)/BST composite films were analyzed using X-ray diffraction, scanning electron microscopy and dielectric spectroscopy, respectively. As the value of x increases from 0.2 to 0.6, the dielectric permittivity (E) of PI/BST composite films increased, while their dielectric loss (tan d) decreased. The PI/Ba0.6Sr0.4TiO3 composite films possessed the larger E of 24 at 102 Hz, which is almost twice higher than that of the PI/Ba0.2Sr0.8TiO3 one. It was attributed to the Maxwell-Wagner behavior between PI matrix and BST ceramic particles, resulting in the larger E of ceramics. Besides, the PI/Ba0.6Sr0.4TiO3 demonstrated the lower tan d of 0.004 at 102 Hz, which showed broad temperature dependence. Therefore, the PI/Ba0.6Sr0.4TiO3 flexible material has a potential application as excellent microwave dielectrics