Polytetrafluoroethylene composites with Zr₂O(PO₄)₂ filler for high-frequency applications: Tailoring dielectric and thermal expansion properties via surface modification

A PTFE-based composite with surface-modified Zr₂O(PO₄)₂ (ZOP) filler was developed for high-frequency applications. • FAS-17 surface modification improves tZOP-PTFE compatibility and filler dispersion while reducing visible defects. • PTFE@tZOP-40 exhibits an ultralow dielectric loss (D f = 5.5 ×10 −4 at 10 GHz) and a reduced CTE of 51.6 × 10 −6 K −1 . With the increasing demand for advanced dielectric materials in high-frequency microwave and millimeter-wave systems, polytetrafluoroethylene (PTFE) has attracted considerable attention due to its low dielectric constant, low dielectric loss, and excellent electrical insulation. However, its high coefficient of thermal expansion (CTE) may cause dimensional instability and reliability issues in high-frequency substrate applications. In this study, zirconium oxophosphate (Zr₂O(PO₄)₂, ZOP), an ultralow-CTE ceramic filler, was incorporated into the PTFE matrix to develop composites with reduced thermal expansion and favorable dielectric performance. To improve the compatibility between hydrophilic ZOP and hydrophobic PTFE, ZOP particles were surface-modified using a fluorinated silane coupling agent to obtain tZOP. The modified tZOP showed improved dispersion in the PTFE matrix and reduced visible defects, contributing to a denser composite microstructure and enhanced thermal dimensional stability. At a filler loading of 40 wt%, the PTFE@tZOP composite achieved a CTE of 51.6 × 10 −6 K −1 , a dielectric constant of 2.83, and a dielectric loss of 5.5 × 10 −4 at 10 GHz. This work demonstrates an effective surface-modification strategy for developing PTFE-based composites with low thermal expansion and favorable dielectric properties for next-generation high-frequency substrates. Download: Download high-res image (185KB) Download: Download full-size image