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

A series of Ba
_x
Sr
_1-x
TiO
₃
(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 (ε) of PI/BST composite films increased, while their dielectric loss (tan δ) decreased. The PI/Ba
_0.6
Sr
_0.4
TiO
₃
composite films possessed the larger ε of 24 at 10
²
Hz, which is almost twice higher than that of the PI/Ba
_0.2
Sr
_0.8
TiO
₃
one. It was attributed to the Maxwell-Wagner behavior between PI matrix and BST ceramic particles, resulting in the larger ε of ceramics. Besides, the PI/Ba
_0.6
Sr
_0.4
TiO
₃
demonstrated the lower tan δ of 0.004 at 10
²
Hz, which showed broad temperature dependence. Therefore, the PI/Ba
_0.6
Sr
_0.4
TiO
₃
flexible material has a potential application as excellent microwave dielectrics.