Radio-Absorbing and Radiating Properties of Lead Ferrotungstate Ceramics

By means of the spark-plasma sintering method, ceramic samples of ferro tungstate (PbFe2/3W1/303, PFW) relaxor ferroelectrics with a grain size of 1–2
$\mu \mathrm{m}$
are manufactured. Energy-absorption spectra of PFW samples are studied by using a microstrip line as a measuring cell in the frequency range of 3.1-12 GHz. Rugged spectra of a resonant behavior, containing 3–4 large (25–40 dB) sharp peaks, are obtained. Absorption spectra are sensitive to external factors such as temperature, uniaxial mechanical pressure, and microstrip coupling coefficient. An exposure to a constant magnetic field at room temperature does not change the spectra either because of the low magnetic field induction
$(\mathbf{B}= 0.375\ \mathbf{T})$
or because of a weak ferromagnetic phenomenon in the studied PFW samples. The three-mode spectrum of the integral radiation of the electric field intensity E and magnetic field induction B are obtained at different heights from the surface of the PFW sample. The experimental data from the present study confirm the presence of polar nanoregions (clusters) in PFW ceramics at a considerable distance from the diffuse phase transition temperature. Absorption spectra of PFW with a large number of resonance-type maxima indicate the existence of various ensembles of oscillators in PFW. Their role can be played by the domain walls of mechanical twins in PFW clusters, which perform elastic oscillations on applying the electromagnetic field to the ceramic sample.