Dielectric spectroscopy of [Pb.sub.1-x][Ba.sub.x][.sub.n][Ti.sub.z][O.sub.3] solid solutions in a wide temperature interval

The dielectric spectra of [Pb.sub.1 x][Ba.sub.x][([Mg.sub.1/3][Nb.sub.2/3]).sub.m][([Zn.sub.1/3][Nb.sub.2/3]).sub.y][([Ni.sub.1/3][Nb.sub.2/3]).sub.n][Ti.s ub.z][O.sub.3] (x = 0-0.15, m = 0.4541, y = 0.0982, n = 0.1477, and z = 0.3) ceramic samples have been studied in wide intervals of temperature (10-873 K) and frequency of the measurement electric field (0.1-1000 kHz). It has been found that an increase in the [Ba.sup.2+](x) content leads to a reduction in the phase transition temperature (from 418 K at x = 0 to 256 K at x = 0.15), to the transition from the normal ferroelectric state to the relaxor ferroelectric one (at x [greater than or equal to] 0.025), and to the disappearance of temperature hysteresis of dependences of the relative dielectric permittivity. It has been hypothesized that a tricritical point is present near x ~ 0.125 in the x-T phase diagram of the studied solid solutions.