Dopant (Mn, Fe, Co and Cu) effects on the structure and dielectric dispersion mechanisms in relaxor PLZT ceramics

The PLZT 8/65/35 compound, commonly known for relaxer behaviour, as well as PLZT 8/65/35+Me compositions (Me = 3d elements (Mn, Fe, Co or Cu)) is examined, a number of different techniques being used: (1) dielectric measurements of complex permittivity epsilon(nu, T, E) at frequencies from 10(-1) to 10(7) Hz in the range of temperatures from 0 to 200 degrees C; (2) Raman scattering (RS), EPR and x-ray diffraction. The behaviour of epsilon(nu, T, E) is interpreted assuming the existence of three different polarization mechanisms, the partial contributions to the dielectric constant of which depend on the dopant concentration and the ranges of frequencies, temperatures or field intensities. Structural criteria are proposed to evaluate the contributions from each of the mechanisms.