The influence of processing on the microstructure and the microwave properties of Co–F-codoped barium strontium titanate thick-films

The influence of processing on the microstructure and the dielectric properties of Co–F-codoped Ba0.6Sr0.4TiO3 (BST) thick-films has been investigated. BST powders with different particle sizes were prepared and applied on alumina substrates by screen-printing. The resulting thick-films were sintered at different holding times and characterized with respect to their microstructure and microwave properties. The microstructure of the thick-films shows a clear dependency on sintering time and initial particle size. In addition to grain growth, the formation of a secondary phase is observed at the interface between substrate and BST with increasing sintering time. The dielectric characterization at microwave frequencies shows an increase of tunability with larger grain size while the dielectric loss is even lowered. This shows the strong influence of the microstructure on the material properties and the possibility of tailoring the material through specific processing.