High-Entropy Ti ⁴⁺ -Containing Perovskite Ceramics with Excellent Electromagnetic Wave-Absorbing Performance via Low-Temperature Sintering

To prepare absorbing materials with strong reflection loss under lower-temperature conditions, multiple elements were introduced into SrFeO3–x based on the design of high-entropy components. The results showed that the absorbing material Sr(Cr1/5Mn1/5Fe1/5Co1/5Ti1/5)O3–x with strong reflection loss could be obtained by the solid-phase method at 1000 °C after Ti4+ was introduced into the B site. It is worth noting that at 1100 °C, the minimum reflection loss (RLmin) of the high-entropy ceramic is −43.43 dB, and the effective absorption bandwidth (EAB) is 5.04 GHz. At 1200–1300 °C, the RLmin values of high-entropy ceramics at 4.60 and 5.00 mm are −50.26 and −53.09 dB, respectively. Ti4+ plays a dual role as a “structural stabilizer” and “electromagnetic property regulator” in high-entropy ceramic absorbing materials. Its high diffusion coefficient realizes low-temperature sintering of materials, and its multiscale effect (lattice distortion and heterogeneous interface) leads to “strong wave-absorbing capacity”. The excellent wave-absorbing performance is also attributed to the lattice distortion and large interface structure. Meanwhile, the design of Ti4+ and other B-site high-entropy elements to construct a magnetic–dielectric cooperative mechanism and oxygen vacancy defect engineering are both key to achieving excellent performance. In addition, high-entropy ceramics containing Ti4+ have high stability, which extends the service life of the material and provides a greater space for practical applications of absorbing materials.