Novel high-entropy cordierite ceramics with both electromagnetic wave absorption and infrared radiation properties via one-step sintering

Abstract

Cordierite is widely used in high-temperature kilns and infrared heating because of its high infrared emissivity. In this study, high-entropy cordierite ceramics were prepared by a one-step sintering process, which extended the other properties of cordierite while reducing the sintering temperature. The phase composition, microstructure, electromagnetic wave absorption properties, and infrared radiation properties of high-entropy cordierite ceramics were investigated successively. The results show that by selecting several common oxides doped in equal amounts and holding the ceramics at 1100 °C for three hours, high-entropy cordierite ceramics (Mg_0.25Fe_0.25Mn_0.25Zr_0.25)₂(Al_0.5Ti_0.5)₄Si₅O₁₈ can be synthesized, and the sintering temperature of which is 200 °C lower than that of conventional cordierite. Compared with cordierite, without wave-absorbing properties, the magnetic oxides, oxygen vacancies, and pores in the high-entropy samples lead to magnetic and dielectric losses, resulting in a minimum reflection loss of −38.21 dB at 4.88 GHz, accompanied by an effective absorption bandwidth (EAB) of 2.56 GHz at a thickness of 4.70 mm. Meanwhile, due to the lattice vibrations and dipole moment changes caused by lattice distortion, the prepared high-entropy cordierite ceramics maintain a high infrared radiation (IR) emissivity above 0.85 at 8–14 μm wavelengths. In addition, MgO, Al₂O₃, SiO₂, and ZrO₂ formed a low eutectic mixture during the sintering process, which reduced the sintering temperature of high-entropy cordierite ceramics. This work is of great significance for expanding the application areas and improving the sintering properties of cordierite ceramics.