High-k and low-loss polymer composites with co-fired Nd and Mg-Ca titanates for 3D RF and microwave printed devices: Fabrication and characterization

Two types of high-permittivity and low-loss flexible composite substrates based on a Polydimethylsiloxane (PDMS) elastomer host matrix reinforced by NdTiO₃ and MgCaTiO₂ microfillers with volume loading concentration up to 25% have been prepared and characterized up to 20 GHz using cavity resonators. The 25% loaded PDMS-MgCaTiO₂ composites with co-fired fillers have exhibited relative permittivity er of ~12.19 and loss tangent tanδ_d <; 0.021 at frequencies up to 20 GHz. Meanwhile, 25% loaded PDMS-NdTiO₃ composites with co-fired fillers have shown a relative permittivity ε_r of ~9.22 and loss tangent tanδ_d <; 0.025 at frequencies up to 17 GHz. A 19.6 GHz microstrip patch antenna was 3D-printed by employing a molded PDMS-MgCaTiO₂ composite substrate and silver ink to form the conductive layer, achieving 20 dB return loss and about 10% bandwidth. Evidently these newly developed polymer-ceramic composites are well suited for applications up to the K-band and are amenable to 3D printing technology.