Refractory Metamaterial Microwave Absorber with Strong Absorption Insensitive to Temperature

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 (TiB 2 ) as unit cells and dielectric alumina (Al 2 O 3 ) 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 Al 2 O 3 spacer and the big enough conductivity of TiB 2 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 TiB 2 and Al 2 O 3 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.