Enhanced electric-field-induced strains in (K,Na)NbO3 piezoelectrics from heterogeneous structures
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Materials Science↗
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Materials Data on NbO3 by Materials Project
NbO3 crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Nb is bonded to twelve equivalent O atoms to form a mixture of corner and face-sharing NbO12 cuboctahedra. There are six shorter (2.24 Å) and six longer (2.37 Å) Nb–O bond lengths. O is bonded in a see-saw-like geometry to four equivalent Nb atoms.
36 MATERIALS SCIENCE↗
Materials Data on Nb2TlO7 by Materials Project
(NbO3)2TlO crystallizes in the orthorhombic Imma space group. The structure is three-dimensional and consists of two TlO ribbons oriented in the (1, 0, 0) direction and one NbO3 framework. In each TlO ribbon, Tl is bonded in a distorted linear geometry to two equivalent O atoms. Both Tl–O bond lengths are 2.08 Å. O is bonded in a bent 120 degrees geometry to two equivalent Tl atoms. In the NbO3 framework, there are two inequivalent Nb sites. In the first Nb site, Nb is bonded to six O atoms to form corner-sharing NbO6 octahedra. The corner-sharing octahedra tilt angles range from 39–40°. There is two shorter (1.97 Å) and four longer (2.02 Å) Nb–O bond length. In the second Nb site, Nb is bonded to six O atoms to form corner-sharing NbO6 octahedra. The corner-sharing octahedra tilt angles range from 38–39°. There are four shorter (2.00 Å) and two longer (2.01 Å) Nb–O bond lengths. There are three inequivalent O sites. In the first O site, O is bonded in a distorted bent 150 degrees geometry to two equivalent Nb atoms. In the second O site, O is bonded in a bent 150 degrees geometry to two equivalent Nb atoms. In the third O site, O is bonded in a distorted bent 150 degrees geometry to two Nb atoms.
36 MATERIALS SCIENCE↗
Materials Data on NbFeO3 by Materials Project
FeNbO3 is (Cubic) Perovskite structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional and consists of one iron molecule and one NbO3 framework. In the NbO3 framework, Nb3+ is bonded to six equivalent O2- atoms to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles are 0°. All Nb–O bond lengths are 2.00 Å. O2- is bonded in a linear geometry to two equivalent Nb3+ atoms.
36 MATERIALS SCIENCE↗
Revisiting Structural and Electromechanical Properties of the Lead-free (K,Na)NbO 3 High-Piezoelectric Material
Having lead-free systems with excellent piezoelectric responses is crucial to the development of environmentally friendly electromechanical applications. In this work, we build an effective Hamiltonian model to explore the promising (K x Na 1–x )NbO 3 system, whose rich phase diagram near x = 50% remains poorly understood meanwhile exhibiting a colossal effective piezoelectric response. Thanks to the numerical implementation of this effective Hamiltonian scheme into a Monte Carlo Metropolis algorithm, we reveal striking features. First, a long-period state can be the ground state at low temperatures for some concentrations while only a short-period conventional polar ground state exists for larger x. Second, the electric field-driven transformation, via a first-order transition, of this long-period state into a short-period polar state creates large electromechanical strains (on the order of the percent) and is likely the origin of the colossal piezoelectric response reported in KNN, for which we evaluate an effective piezoelectric coefficient of several thousands of pC/N.
(K,Na)NbO3↗