Ferroelectric and magnetic properties in (1−x)BiFeO₃–x(0.5CaTiO₃–0.5SmFeO₃) ceramics

Abstract

Multiferroic ceramics were prepared and characterized in (1−x)BiFeO3–x(0.5CaTiO3–0.5SmFeO3) system by a standard solid‐state reaction process. The structure evolution was investigated by X‐ray diffraction and Raman spectrum analyses. The refinement results confirmed the different phase assemblages with varying amounts of polar rhombohedral R3c and nonpolar orthorhombic Pbnm as a function of the substitution content. In the compositions range of 0.2≤x≤0.5, polar R3c and nonpolar Pbnm coexisted, which was referred to polar‐to‐nonpolar morphotropic phase boundary (MPB). According to the dielectric and DSC analysis results, the ceramics with x≤0.2 changed to diffused ferroelectric, and the ferroelectric properties were enhanced significantly. Two dielectric relaxations were detected in the temperature range of 200‐300 K and 500‐700 K, respectively. The high‐temperature dielectric relaxation was attributed to the grain‐boundary effects. While the low temperature dielectric relaxation obtained in the samples with x=0.3‐0.5 was related to the charge transfer between Fe2+ and Fe3+. The magnetic hysteresis loops measured at different temperature indicated the enhanced magnetic properties in the present ceramics, which could be attributed to the suppressed cycloidal spin magnetic structure by Ti ions. In addition, the rare‐earth Sm spin moments might also affect the magnetic properties at relatively lower temperature.

Disrupting long-range polar order with an electric field

“…We reveal this unusual phase transition in a lead-free relaxor composition of [(Bi 1/2 Na 1/2 ) 0.95 Ba 0.05 ] 0.98 La 0.02 TiO 3 (BNT2La) in which a ferroelectric phase can be readily formed during electric poling [30,31]. The induced ferroelectric phase remains metastable upon field removal.…”

“…1. The virgin state ceramic is a non-ergodic relaxor at room temperature [30], as indicated by the strong frequency dispersion in the dielectric behavior ( Fig. 1a) and representative nanometer-sized domains in its microstructures (Fig.…”

Giant strain with low cycling degradation in Ta-doped [Bi1/2(Na0.8K0.2)1/2]TiO3 lead-free ceramics

“…Download to IP: 129.186.176.188 On: Mon, 12 Dec tilting. 8,11,18,19 Therefore, the rhombohedral R3c and tetragonal P4bm phases coexist in the BNT-100xTa (1.0 x 3.0) ceramics in the form of nanometer-sized polar domains. It is interesting to observe that the 1 = 2 {ooe}-type superlattice spots are much stronger than the 1 = 2 {ooo}-type spots in the [112] diffraction patterns, indicating that the tetragonal phase is dominant in these compositions.…”

“…6 Among the lead-free solid solution systems reported in the literature, (Bi 1/2 Na 1/2 )TiO 3 -based compositions 7,8 seem to be most likely to develop ultrahigh strains under applied electric fields. [9][10][11] For example, a 2007 study by Zhang et al reported a very large electrostrain of 0.45% in the polycrystalline ceramic 0.92(Bi 1/2 Na 1/2 )TiO 3 -0.06BaTiO 3 -0.02 (K 0.5 Nb 0.5 )NbO 3 under an applied field of 80 kV/cm. 9 Since then, even higher strains (0.48%) have been reported, [12][13][14][15] primarily in modified [Bi 1/2 (Na 1-x K x ) 1/2 ]TiO 3 compositions.…”

Design and development of high-performance lead-free piezoelectric ceramics

“…49,50,51 The ternary system BNT-BKT-BT, for example, has been thoroughly investigated due to the excellent piezoelectric properties with a d 33 Sintering was conducted at 1150 o C for 3 hours.…”