Medium dielectric constant and low‐loss PTFE composites filled with MgO‐LiF co‐doped Li₂TiO₃ particles

Abstract

In this work, we presented a simple strategy to fabricate medium dielectric constant and low-loss composites for microwave substrate applications. MgO-LiF co-doped Li 2 TiO 3 (LT) powders were fabricated by the solid-state reaction route and modified by perfluorooctyltriethoxysilane (F8261). The LT/polytetrafluoroethylene (PTFE) composites were fabricated by cold pressing and hot treatment. The XPS and contact angle analysis indicated that the fluorinated group was introduced to LT particle successfully. The effects of modified LT powders content on the dielectric, thermal, and mechanical properties of composites were investigated. As the modified LT content increases, the dielectric constant, dielectric loss, and temperature coefficient of dielectric constant (τ ε ) increase while the bending strength and coefficient of thermal expansion (CTE) decrease, which is attributed to the higher dielectric constant of LT ceramic, more pores, stable τ ε of LT ceramic, interface defects and low CTE of LT ceramic, respectively. The composites with 60 wt % LT exhibit the best microwave dielectric properties: ε r = 6.8, tanδ = 0.001, τ ε = −29.6 ppm C −1 at 8 GHz and acceptable coefficient of thermal expansion (28.3 ppm C −1 ). Therefore, modified LT powders filled PTFE composites are potential materials for high-frequency microwave substrate applications.

MPPE/SEBS Composites with Low Dielectric Loss for High-Frequency Copper Clad Laminates Applications

“…However, Figure 4 b shows that the modified powders are well-distributed. In other words, the coupling agent decreases the interaction among LT powders, and improve the compatibility of filler and polymer [ 14 , 20 ]. The water contact angle is measured and shown in Figure 4 c–f.…”

“…In order to decrease dielectric loss and modify the dielectric constant (Dk) as well as coefficient of thermal expansion (CTE) of polymeric composites, different inorganic fillers were added into the resin matrix [ 13 , 14 , 15 ]. In the light of our previous works, Li 2 TiO 3 -MgO-LiF (LT) ceramic is an extremely good additive with Dk of 23.2, Df of 0.00012 at 8 GHz [ 16 ].…”

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