Surface-modified Zn_0.5Ti_0.5NbO₄ particles filled polytetrafluoroethylene composite with extremely low dielectric loss and stable temperature dependence

Polymer-ceramic composites are widely applied in microwave substrate materials due to the excellent dielectric properties and simple preparation process recently. Polytetrafluoroethylene-based (PTFE) composites filled with Zn_0.5Ti_0.5NbO₄ (ZTN) ceramic particles were fabricated by hot-pressing. The particles were modified by C₁₄H₁₉F₁₃O₃Si to enhance the interface compatibility between PTFE and ZTN powders, which was characterized by X-ray photoelectron spectroscopy (XPS) and contact angle. The surface characteristic of particles transformed into hydrophobicity and tight microstructure as well as better dielectric properties were obtained after the surface modification. The microstructure, dielectric, thermal, mechanical properties, and water absorption of the composites concerning ZTN content were investigated. Modified ZTN/PTFE composites with 50 vol% ZTN particles exhibit excellent dielectric properties with a high dielectric constant of 8.3, an extremely low dielectric loss of 0.00055 at 7 GHz, and a stable temperature coefficient of the dielectric constant of -12.2 ppm/℃. All the properties show modified ZTN particles filled PTFE composite is the potential material for microwave substrate application.