Refractory Metamaterial Microwave Absorber with Strong Absorption Insensitive to Temperature

Abstract The so far developed microwave absorbers all exhibit dramatically changing absorption with temperature, hindering them from working in a broad temperature range. Here, a refractory metamaterial microwave absorber (rfMMA) with the absorption insensitive to temperature by using refractory ceramics of conductive titanium diboride (TiB₂) as unit cells and dielectric alumina (Al₂O₃) as a spacer is designed and experimentally demonstrated. The as‐proposed rfMMA shows strong microwave absorption in a wide temperature range. A definite physical equivalent circuit model that tightly links the structural and constitutive parameters of the rfMMA to its absorption properties is established. It reveals that with a stable configuration of the as‐proposed rfMMA, the little temperature effect on the permittivity of Al₂O₃ spacer and the big enough conductivity of TiB₂ unit cells ensure an almost constant absorption in a wide temperature range, avoiding the temperature‐sensitive problem of traditional refractory absorbers. Moreover, the excellent chemical stability of TiB₂ and Al₂O₃ at high temperature further ensures the long‐term service of the as‐fabricated rfMMA, as confirmed by experiments. This work provides a route to achieve refractory microwave absorbers with strong absorption at a wide temperature range, and illustrates a bright prospect of the all‐ceramic metamaterial absorbers in high temperature applications.