High-Performance Bi_0.5Na_0.5TiO₃ Single Crystals Grown by High-Oxygen-Pressure Flux Method

Abstract

High-P O2 (oxygen pressure) crystal growth is developed for Bi 0:5 Na 0:5 TiO 3 single crystals based on defect chemistry at high temperatures. Thermogravimetric analysis shows that the vacancy formations of Bi and O at high temperatures are controlled by the surface reaction (oxygen desorption), which is suppressed at a higher P O2 . Bi 0:5 Na 0:5 TiO 3 crystals grown at a P O2 of 1 MPa exhibit a saturated remanent polarization of 44 mC/cm 2 along [110] cubic , suggesting a spontaneous polarization of 54 mC/cm 2 along [111] cubic (polar direction) of rhombohedral Bi 0:5 Na 0:5 TiO 3 . High-P O2 heat treatments are proposed to be effective for fabricating high-quality and high-performance ferroelectric/piezoelectric devices using Bi-based ferroelectric oxides.

Giant electric-field-induced strains in lead-free ceramics for actuator applications – status and perspective

“…In fact, the attention to BNT-based materials also, in part, rooted from a success in developing single crystals with giant strains [51,196]. Attempts to grow lead-free single crystals have already been made in KNN-based [197][198][199][200][201], BNTbased [51,196,[202][203][204][205][206][207][208][209][210][211][212][213][214], and other systems [215,216] so far. Although excellent and intriguing properties have been reported in the reported lead-free single crystals in the literature, it seems that reported properties and characteristics lack consistency.…”

Polarization and leakage current properties of bismuth sodium titanate ceramic films deposited by aerosol deposition method

“…Based on this standpoint, high-P O2 (partial oxygen pressure) crystal growth in order to be suppressed Bi vaporization is demonstrated to be effective for enhancing the polarization and piezoelectric properties of BNT single crystals. 16) In a ceramic processing based on solid-state reaction, BNT has been sintered at a high temperature of around 1200°C to obtain dense ceramics. Such a high-temperature treatment induces a vaporization of Bi with a high vapor pressure, which leads to a formation of vacancies of Bi and oxygen.…”

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

“…Using thermogravimetric analyses we have confirmed that this annealing treatment does not cause a significant Bi loss in the crystals. 87) For the measurements of polarization hysteresis and E-induced strain, the annealed crystals were cut into 0.150.25-mm-thick plates, and Pt electrodes were sputtered onto the cut surfaces. Polarization (P) hysteresis loops were measured at 25°C along the pseudocubic [001] direction using a ferroelectric test system (Toyo Model 6252 Rev.…”