Investigation of Dielectric Response, Conductivity, and Thermostimulated Depolarization Current in PbNi.sub.1/3Nb.sub.2/3O.sub.3 Relaxor Ferroelectric

In this paper, the results of a study of the temperature dependences of dielectric response and conductivity at direct and alternating current in single crystals of PbNi.sub.1/3Nb.sub.2/3O.sub.3 (PNN) relaxor ferroelectric in a wide frequency range (from 10 Hz to 100 kHz) and temperature range (80-750 K) are presented. Dielectric response anomalies in the form of broad frequency-dependent maxima are observed near 153 and 730 K. The ther-moactive type of conductivity is found under the direct current and activation energies E.sub.a = 770 meV for T > 310 K and E.sub.a = 23 meV for T < 310 K are determined. The results of the conductivity analysis give grounds to assume the existence of local conductivity in the low temperature range. It is shown that the conductivity behavior changes from local to bulk conductivity with the increase in temperature starting from 350 K. The temperature range of existence of residual polarization (observed at T < 130 K) is determined by measuring the thermostimulated depolarization current.