Synthesis and electromagnetic wave reflectivity of Si3N4 ceramic with gradient Fe3O4 distribution

A Si3N4 ceramic with gradient distribution of tri–iron tetroxide (Gradient–Si3N4–Fe3O4) was fabricated with a combined technique of chemical precipitation and directional infiltration. Electromagnetic wave could enter Gradient–Si3N4–Fe3O4 with little reflection because of weak impedance mismatch at its surface. Also the electromagnetic wave entering the Gradient–Si3N4–Fe3O4 propagated with small reflection due to continuous and gradual change of impedance resulting from the gradient Fe3O4 distribution, and was absorbed completely by Fe3O4 of the gradient structure.