Tunable dielectric properties of porous ZnAl₂O₄ ceramics for wave-transmitting devices

To develop high-performance ceramic devices with a low dielectric constant and low dielectric loss, porous ZnAl₂O₄ ceramics were fabricated by combining a pore-forming agent and partial sintering using ZnAl₂O₄ particles with an average size of 80 nm as the precursor and polyethylene glycol (PEG) as the pore-forming agent. The microstructure and dielectric properties of the porous ZnAl₂O₄ ceramics were investigated. As the PEG content increased from 10 to 24 wt%, the porosity of the ceramics increased from 53.80 to 63.30%, the thermal conductivity decreased from 0.446 to 0.212 W/m K, the compressive strength decreased from 15.74 to 11.75 MPa, and the dielectric constant decreased from 5.63 to 3.74, respectively. The increase in porosity with increasing pore-forming agent contributed to the low dielectric constant and low thermal conductivity while maintaining good mechanical properties. Moreover, the uniform pore structure of the ceramics supported the low dielectric loss. The prepared porous ZnAl₂O₄ ceramics can be used as a new type of wave-transmitting material.