Emergence of high piezoelectricity from competing local polar order-disorder in relaxor ferroelectrics

Abstract

Relaxor ferroelectrics are known for outstanding piezoelectric properties, finding a broad range of applications in advanced electromechanical devices. Decoding the origins of the enhanced properties, however, have long been complicated by the heterogeneous local structures. Here, we employ the advanced big-box refinement method by fitting neutron-, X-ray-based total scattering, and X-ray absorption spectrum simultaneously, to extract local atomic polar displacements and construct 3D polar configurations in the classical relaxor ferroelectric Pb(Mg1/3Nb2/3)O3–PbTiO3. Our results demonstrate that prevailing order-disorder character accompanied by the continuous rotation of local polar displacements commands the composition-driven global structure evolution. The omnidirectional local polar disordering appears as an indication of macroscopic relaxor characteristics. Combined with phase-field simulations, it demonstrates that the competing local polar order-disorder between different states with balanced local polar length and direction randomness leads to a flattening free-energy profile over a wide polar length, thus giving rise to high piezoelectricity. Our work clarifies that the critical structural feature required for high piezoelectricity is the competition states of local polar rather than relaxor.

Chemical Design of Pb-Free Relaxors for Giant Capacitive Energy Storage

“…However, the direction of the polar displacement vectors changes drastically (Figure d). Such a composition-driven local order–disorder characteristic has recently been observed in other perovskite-type ferroelectric systems. , In x = 0, the Bi displaces mainly along the [001] c , which agrees well with the long-range T symmetry. While the directions of the Bi polar displacement vector are highly disordered in x = 0.15, and a similar change also occurs in Ti (Figure S10).…”

Outstanding Energy-Storage Density Together with Efficiency of above 90% via Local Structure Design

“…With regard to the local structure analysis, information related to the chemical bonding at a subnanoscale can be obtained, which effectively compensates for the shortcomings of the diffraction data in the analytical scale and provides deep insight into the understanding of the intrinsic structure. The neutron total scattering combined with recently developed reverse Monte Carlo (RMC) methods was further performed. − The RMC algorithm could be used to fit the real-space data G ( r ) and reciprocal-space S ( Q ) data simultaneously based on a 20 × 20 × 20 perovskite supercell (Figure a, ∼80 Å × 80 Å × 80 Å). As shown in Figure b,c, both real-space data G ( r ) and reciprocal-space data S ( Q ) of BT and BNT–50BT were well fitted.…”

Local structure heterogeneity in unique tetragonal BaTiO3-based relaxor featuring ultrahigh electrostrictive effect

“…[29][30][31] Furthermore, when combined with the big-box modelling method based on the reverse Monte Carlo (RMC) algorithm, 32 the A/B-site positions and displacement distributions in perovskites can be obtained. 15,29,33 Herein, we report the evolution of local structures with increasing temperature in a unique tetragonal 0.85BaTiO 3 -0.15Bi 0.5 Li 0.5 TiO 3 (BT-15BLT) relaxor. The T distortions at different scales were revealed by using X-ray diffraction and neutron total scattering.…”

“…[1][2][3][4][5][6][7][8][9][10] The fascinating properties of RFEs are thought to be linked to their heterogeneous polar structures. [11][12][13][14][15][16][17] Initially, RFEs were studied using models based on compositional uctuations with deviations from completely disordered solid solutions. [18][19][20][21] The widely accepted theory for explaining the dielectric anomaly is rooted in the local polarization correlations at the nanoscale, known as polar nanoregions (PNRs).…”

“…29–31 Furthermore, when combined with the big-box modelling method based on the reverse Monte Carlo (RMC) algorithm, 32 the A/B-site positions and displacement distributions in perovskites can be obtained. 15,29,33…”