Thinner electromagnetic wave absorbers using ferroelectric substances

Two types of electromagnetic wave absorbers using ferroelectric materials have been studied. Ferroelectric materials are superior to ferromagnetic ones at frequencies in the above gigahertz range, because their permeability does not decrease as much. In one type of absorber, a resistive film was placed in front of the ferroelectric material. In the other, a ferroelectric layer was placed in front of a soft-magnetic layer. Placing a resistive film in front of the ferroelectric material made it possible to design wave absorbers even though the real and imaginary parts of the permittivity did not fulfill the matching condition. Both absorbers could be made thinner than conventional carbonyl iron-loaded rubber ones and still work well at frequencies above giga-hertz. Furthermore, the matching frequency can reduce to the quasi-microwave-band range by placing a ferroelectric layer in front of the carbonyl iron-loaded rubber.