Detecting depinning of polar nanoregions under dc external electric field in canonical relaxor ferroelectric Pb(Mg_1/3Ta_2/3)O₃ via acoustic emission

Abstract

Phone: þ972 2 549 4665, Fax: þ972 2 658 5117Canonical relaxor ferroelectric Pb(Mg 1/3 Ta 2/3 )O 3 single crystals were studied via acoustic emission in temperature range of 180-250 K covering their dielectric constant temperature maximum at T m % 202 K, and under dc external electric fields up to 1.2 kV cm À1 . The dependence of T m on dc external electric field exhibits a nonlinear behavior, characteristic of relaxors: it initially decreases, attains a sharp minimum at the threshold field of 0.25 kV cm À1 and then starts to increase, as the field enhances. The count rate of the accompanying acoustic emission exhibits two maxima: at 0.1 and 0.6 kV cm À1 . The latter obviously corresponds to the end critical point, also characteristic of relaxors, while the former is attributed to a polar nanoregions depinning field at which the polar nanoregions start to be switched off from the intrinsic random electric fields to the dc external electric field. These data are discussed from the viewpoint of competition between random electric fields and an external electric field when affecting the polar nanoregions.

Effect of some dopants on temperature of high-temperature phase transitions of Na0.5Bi0.5TiO3-0.06BaTiO3 lead-free relaxor ferroelectrics ceramics seen via acoustic emission

“…Also the AE has detected the phase transition to the PE Pm3m phase, located above the T m and referred to as T p , for all the compounds, which has previously been detected by AE in NBT-6BT only [14,40], at that the T p is not accompanied by any dielectric anomaly in accordance with the data [14,40]. It is necessary to stress that the AE detection at T m might be due to two reasons: an interaction of the PNRs [16,18], as it is earlier detected at T m in canonical Pb(Mg 1/3 Ta 2/3 )O 3 crystals [55], as well as the phase transition P 4bm-P 4/mbm [17]. To understand what process really occurs one need look at the dependence of shift of T m when incorporating the dopants.…”