High-strength ceramic foams with ultralow dielectric constant and loss in terahertz frequency region

Sixth generation (6G) wireless networks operating in terahertz frequency region are significant solutions to the increasing number of telecommunication devices and the demand for faster data transmission. However, few dielectric materials exhibiting an ultralow relative dielectric constant (ε_r), loss tangent (tanδ), and high mechanical strength are found suited for 6G telecommunication. In this study, we developed lightweight ceramic foams by directly sintering glass hollow spheres. The effects of sintering temperatures on their mechanical performance, and terahertz optical and dielectric properties were systematically investigated. The final compositions of ceramic foams contain glass, cristobalite, quartz, and wollastonite. The crystalline content increases with increasing sintering temperature. The ceramic foams sintered at low temperatures of 700–850°C exhibit a high porosity ranging from 74.6% to 87.3%, ultralow ε_r ranging from 1.41 to 1.83, and tanδ of ∼0.011 at 0.5 THz, as well as high compressive strength ranging from 10.1 to 27.4 MPa, which could be promising materials for 6G telecommunication.