Combined Real-Time Study of Dielectric Response and Piezoresponse of Pb(Mg 1/3 Nb 2/3 )O 3 Relaxor in an Electric Field
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OELECTRICS
Combined Real-Time Study of Dielectric Response and Piezoresponse of Pb(Mg1/3Nb2/3)O3 Relaxor in an Electric Field A. F. Vakulenkoa,*, S. B. Vakhrushevb, and E. Yu. Korolevab a Peter
the Great St. Petersburg Polytechnic University, St. Petersburg, Russia b Ioffe Institute, St. Petersburg, Russia *e-mail: [email protected]
Received April 29, 2020; revised April 29, 2020; accepted May 5, 2020
Abstract—A method of synchronous measurement of the piezoresponse signal and electrical impedance when studying the processes of polarization switching in an external electric field has been described. Using the developed technique, the processes of switching ferroelectric (FE) phase of lead magnoniobate induced by an electric field are studied. It is shown that a polydomain structure with a weak piezoresponse is formed during the initial appearance of the FE phase. A change in the direction of the external field leads to polarization switching, and the switching process passes through an intermediate glass-like phase. Training the sample by multiple switching leads to a sharp increase in piezoresponse, which can be associated with a single-domain state formation. Keywords: ferroelectrics, relaxors, piezoresponse, phase transitions DOI: 10.1134/S1063783420100340
1. INTRODUCTION Ferroelectrics-relaxors (named first “ferroelectrics with a blurred phase transition”) were discovered more than 60 years ago and are being actively investigated. The reason for the allocation of the newly discovered materials into a separate group was, first of all, their special dielectric properties: instead of an expressed critical peak in the dielectric constant, a wide maximum is observed, the position and magnitude of which significantly depend on the measurement frequency. Structural studies of relaxors and, in particular, the “canonical” compound – lead magnoniobate Pb(Mg1/3Nb2/3)O3 (PMN), did not reveal any deviations from cubic symmetry down to helium temperatures. PMN and its solid solutions with normal ferroelectrics are actively studied during several decades [1–7]. The obtained important theoretical and experimental results on the dielectric and piezoelectric properties of these materials made possible to achieve great progress in understanding the physical properties of such compounds. The main results are presented in reviews [8, 9] and references therein. It should be noted that there is still no clear definition of relaxor materials (or relaxor phenomena), despite more than half a century of the history of research. One of the most important features that distinguishes them from classical dipole glasses is the existence of an electric-field-induced phase transition to an ordered ferroelectric phase, which is stable in a certain temperature range. The transition to the ferro-
electric phase can only be achieved in the fields above a certain threshold value (about 2.2 kV/cm in the case of PMN for the field in the (111) direction) [10, 11]. In the cooling mode in a field (FC), the phase transition occurs quickly, while when t
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