Nonergodic state of relaxation ferroelectric Cd2Nb 2O7 in a constant electric field

Authors:

• N.N. Kolpakova,
• Piotr Czarnecki

Abstract

The temperature dependence of the residual polarization of the nonergodic relaxation state (NERS) obtained from the measurements of pyroelectric current during zero-field heating (ZFH) in the temperature interval from 10 to 295 K is investigated for the Cd₂Nb₂O₇ relaxation system in two cases: (1) after sample cooling in a constant electric field E (FC) from T = 295 K to a preset temperature, which is much lower than the "freezing" temperature of the relaxation state (T_f ≈ 182 K), field removal, and subsequent cooling in zero field (ZFC) to T = 10 K and (2) after ZFC from T = 295 K to the same temperature below T_f, application of the same field, and FC to T = 10 K. The behavior of the P _r^FC(T) and P_r^ZFC(T) dependences is analyzed. In the field E < 2 kV/cm, the P_r^ZFC curves as functions of 1/T have a broad low-intensity peak in the region T ≈ T _f, which vanishes in stronger fields, when the P_r^FC(1/T) curves intersect at T ≈ T_f and have no anomalies. The difference in the behavior of P_r^ZFC(T) and P_r^FC(T) indicates the difference in the nature of NERS formed during ZFC and FC of the system upon a transition through T_f. In the ZFC mode, NERS exhibits glasslike behavior; in the FC regime, features of the ferroelectric behavior even in the weak field. Analogous variations of P_r^ZFC(T) and P_r^FC(T) in a classical ferroelectric KDP are also given for comparison. © 2005 Pleiades Publishing, Inc.