Temperature-insensitive microwave absorption of TiB2-Al2O3/MgAl2O4 ceramics based on controllable electrical conductivity
The design of the high-temperature microwave absorbing materials (MAMs) with temperature-insensitive and considerable microwave absorption (MA) capacity is a tremendous challenge. TiB 2 -Al 2 O 3 /MgAl 2 O 4 MAMs are prepared by the spark plasma sintering (SPS). Further, the influences of the Al 2 O 3 content on the flexural strength, thermal stability, high-temperature electrical conductivity, dielectric and MA properties are discussed. The results show that the Al 2 O 3 content is associated with flexural strength, high-temperature thermal stability, electrical conductivity, dielectric and MA properties. Meanwhile, the temperature-insensitive and considerable MA properties with the minimum reflection loss (RL min ) ranging from −19.4 to −14.3 dB and the effective absorption bandwidth (EAB, RL<−5 dB) of 3.19–3.55 GHz are attained at 25°C–700°C in 8.2–12.4 GHz as the Al 2 O 3 content increases from 70.6 wt% to 80.6 wt%. This is ascribed to the compensating effect of the positive and negative temperature coefficient materials on the high-temperature electrical conductivity as well as the co-play of the dipolar and interfacial polarization at elevated temperatures. Consequently, TiB 2 -Al 2 O 3 /MgAl 2 O 4 ceramics exhibit the ideal prospect as the high-temperature MAMs.
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