Enhanced polarization switching in ferroelectric Bi_0.5Na_0.5TiO₃ single crystals by defect control

Abstract

Single crystals of ferroelectric (Bi,Na)TiO 3 (BNT) were grown by the top-seeded solution growth (TSSG) method at a high oxygen pressure of 0.9 MPa using Pt crucibles and their conductivity (leakage current) and polarization properties were investigated at 25 8C along h100i cubic . The platinum concentration ([Pt]) in BNT crystals was controlled by using different kinds of Na salts in flux. It is shown that the conductivity of BNT crystals is governed by Bi vacancies for crystals with a [Pt] less than approximately 4000 ppm and by Pt impurities for ones with a higher [Pt].Photo and polarization hysteresis of a high-quality (Bi,Na)TiO 3 ferroelectric single crystal. Enhanced polarization switching (a large remanent polarization and a low coercive field) was achieved by defect control during the crystal growth.

Polarization Rotation and Monoclinic Distortion in Ferroelectric (Bi0.5Na0.5)TiO3–BaTiO3 Single Crystals under Electric Fields

“…The direction of E, i.e., the axis normal to the crystal plates was set to be along the <001> pc direction. SR-XRD data were collected with a transmission geometry using a large cylindrical two-dimensional imaging plate (IP) camera with a 1/4χ three-axis goniometer at BL02B1 in the SPring-8 synchrotron radiation facility [50][51][52][53]. A high SR energy of 35 keV [wavelength: 0.035313(2) nm for BNT and 0.035345(2) nm for BNT-5%BT] was adopted so that X-rays with a high transmission ratio could penetrate through the crystals and that a high-angle diffraction pattern could be observed.…”

Polarization Switching Dynamics of Ferroelectric (Bi_0.5Na_0.5)TiO₃ Single Crystals

“…It has been reported that Na 2 CO 3 promotes a dissolution of Pt from the Pt crucible into the solution, resulting in a higher [Pt] and that the [Pt] value in BNT crystals can be controlled by the Na 2 CO 3 content in the flux used for crystal growth processes. [21] These results suggest that the Pt impurity plays a partial role in the defect structure in the BNT crystals. Pöykkö and Chadi [22] have suggested that Pt is substituted at the Ti 4+ site in PbTiO 3 as Pt 2+ (Pt Ti ″ )…”

Enhanced polarization properties of ferroelectric (Bi_1/2Na_1/2)TiO₃&ndash;Ba(Mg_1/3Nb_2/3)O₃ single crystals grown under high-pressure oxygen atmosphere

“…These particles were found to cause no significant influence upon the electrical properties of the crystal. 86) The compositions of the crystals were analyzed by X-ray fluorescence (XRF), showing that the both crystals obtained by the two methods have a BMN composition (x) of 4%. Hereafter, the crystals are denoted by the Po 2 during the crystal growth, i.e., the flux method by 'Po 2 = 0.02 MPa' and the high-Po 2 TSSG method by 'Po 2 = 0.9 MPa'.…”