Correlation of the microstructure and microwave properties of Ba0.6Sr0.4TiO3 thick-films

The influence of the microstructure of screen-printed Ba0.6Sr0.4TiO3 ceramic thick-films on their microwave properties has been investigated. The Ba0.6Sr0.4TiO3 powders were synthesized through a sol–gel route. The spray-dried precursors were calcined at different temperatures. Scanning electron microscopy images and BET measurements revealed the primary particle size of calcined powder depending on the calcination temperature. The Ba0.6Sr0.4TiO3 thick-films showed different microstructure after sintering due to the use of two different calcined BST powders as well as varying the sintering conditions. Permittivity, dielectric loss and tunability of thick-films were characterized with coplanar waveguide structures up to 40 GHz. A correlation of microstructure and microwave properties of the thick-films has been observed. Particularly the tunability could be improved by an optimized microstructure.