A low-loss and medium dielectric permittivity SrTiO3/HIPS composite for rapid prototyping of next-generation microwave devices

<p>Composite polymer/ceramic filaments for material extrusion-based fused filament fabrication (FFF) additive manufacturing, using strontium titanium oxide (SrTiO3) ceramic fillers and high impact polystyrene (HIPS) thermoplastics were produced and their dielectric and physical properties characterised for the first time. Relative permittivity (ε<em>r</em>), quality factor (<em>Q × f</em>) and dielectric loss (<em>tanδ</em>) were measured as a function of ceramic solids loading (vol%) at 5 GHz. <em>εr</em> = 4.6, <em>Q × f =</em> 38,378 GHz and dielectric loss <em>tanδ</em> = 0.001 were obtained for a SrTiO3/HIPS ceramic polymer composite, with 15 vol% (46 wt%) solids loading. A Plackett–Burman design of experiments was used to optimize the printing process of the ST/HIPS composites. The results of this optimisation helped achieve 3D printed parts with near-full density (99 %) and <em>εr</em> = 5.3, <em>tanδ</em> = 0.001. The composite materials exhibit reduced dielectric losses compared with commercially available feedstocks for FFF that are currently used for functional prototyping in the radiofrequency and telecommunications industry. </p>