Issue 17, 2020

Evidence of phase coexistence in hydrothermally synthesized K0.5Na0.5NbO3 nanofibers

Abstract

The argument of phase coexistence in the lead-free piezoelectric perovskite K0.5Na0.5NbO3 (KNN) has led to significant discrepancies in the interpretation of its exact crystalline structure in the literature. In this work, the structural details of hydrothermally prepared KNN nanofibres and microcubes were investigated by a combination of high resolution transmission electron microscopy (TEM), solid-state 23Na and 93Nb nuclear magnetic resonance (NMR) spectroscopy and two-dimensional 23Na 3QMAS NMR. Although powder X-ray diffraction yielded an average orthorhombic structure for both morphologies, high resolution TEM revealed mixed phases of orthorhombic (O) and monoclinic (M) symmetry with a growth direction of [001] and [110], respectively, in individual KNN nanofibres. Consistent with the TEM analysis, solid-state 23Na NMR indicated a distribution of multiple Na sites in the KNN nanofibers, which were not observed in the KNN microcubes. This study provided microscopic evidence of phase coexistence in KNN nanofibers and suggested that a two-phase concomitant state might be highly dependent on the size and morphologies of the KNN nanostructures.

Graphical abstract: Evidence of phase coexistence in hydrothermally synthesized K0.5Na0.5NbO3 nanofibers

Supplementary files

Article information

Article type
Paper
Submitted
28 Dec 2019
Accepted
15 Apr 2020
First published
16 Apr 2020

J. Mater. Chem. A, 2020,8, 8731-8739

Evidence of phase coexistence in hydrothermally synthesized K0.5Na0.5NbO3 nanofibers

M. B. Ghasemian, A. Rawal, Z. Shahrbabaki, Q. Zhang, T. Lu, Y. Liu and D. Wang, J. Mater. Chem. A, 2020, 8, 8731 DOI: 10.1039/C9TA14153G

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