Dielectric properties of BST/polymer composite

A composite of barium strontium titanate (BST) and thermoplastic cyclic olefin copolymer (COC) was investigated with different BST loadings using common and nanosize ceramic powders. The relative permittivity and loss tangent of the composites were measured as a function of loading at 1 GHz and as a function of temperature at 0.1 MHz. A relative permittivity of 6.0 and a loss tangent of 0.0009 at 1 GHz (room temperature) were obtained for a BSTc-COC composite with 25 vol.% loading using common-size particles of BST. The values for a BSTn-COC composite loaded with 25 vol.% of nanosize BST particles were 7.3 and 0.0023, respectively. A modified Lichtenecker logarithmic equation showed good correspondence with measured relative permittivity of the BSTc-COC composite, but especially at a higher loading level, the model failed with the BSTn-COC composite.