Band gap narrowing in ferroelectric KNbO 3 -Bi(Yb,Me)O3 (Me=Fe or Mn) ceramics

Abstract

The direct optical bandgap in ferroelectric KNbO3-Bi(Yb,Me)O3 (Me = Fe or Mn) ceramics fabricated by the solid state reaction method varies from 3.2 eV for KNbO3 down to 2.2 eV for 0.95KNbO3-0.05BiYbO3, as revealed by optical spectroscopic ellipsometry. This narrowing of bandgap is accompanied by an apparent increase of the room-temperature relative permittivity from 320 for KNbO3 to 900 for 0.95KNbO3-0.05BiYbO3. All compositions studied exhibit dielectric anomalies associated with structural phase transitions, and their ferroelectric nature is corroborated by the presence of a sharp mixed mode (at ∼190 cm−1) and by a Fano-type resonant dip in their Raman spectra.

Metadata

Authors/Creators:	Pascual-Gonzalez, C. Schileo, G. Feteira, A.
Copyright, Publisher and Additional Information:	© 2016 AIP Publishing. Reproduced in accordance with the publisher's self-archiving policy.
Dates:	Accepted: 14 September 2016 Published (online): 28 September 2016 Published: 26 September 2016
Institution:	The University of Sheffield
Academic Units:	The University of Sheffield > Faculty of Engineering (Sheffield) > Department of Materials Science and Engineering (Sheffield)
Depositing User:	Symplectic Sheffield
Date Deposited:	29 Sep 2017 12:41
Last Modified:	28 Sep 2018 00:38
Published Version:	https://doi.org/10.1063/1.4963699
Status:	Published
Publisher:	AIP Publishing
Refereed:	Yes
Identification Number:	https://doi.org/10.1063/1.4963699

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Band gap narrowing in ferroelectric KNbO 3 -Bi(Yb,Me)O3 (Me=Fe or Mn) ceramics

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