University of Oulu

Yang Bai, Counterfeit band gaps caused by microstructural voids in photo-ferroelectric ceramics, Open Ceramics, Volume 5, 2021, 100079, ISSN 2666-5395,

Counterfeit band gaps caused by microstructural voids in photo-ferroelectric ceramics

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Author: Bai, Yang1
Organizations: 1Microelectronics Research Unit, Faculty of Information Technology and Electrical Engineering, University of Oulu, FI-90014, Oulu, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 1.9 MB)
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Language: English
Published: Elsevier, 2021
Publish Date: 2021-04-14


In recent years, conventional wide band gap ferroelectric ceramics have been engineered by doping to obtain reduced band gaps. The band gaps in these engineered ceramics are usually determined according to the optical absorption measurement. However, this raises a potential problem in the research of these presumed narrow band gap ferroelectric ceramics as the results of the absorption measurement may give incorrect information of band gaps. This paper demonstrates how microstructural voids, i.e. micron-sized intra- and inter-granular pores in the ceramics formed with improper sintering conditions, can create additional absorption peaks thus leading to counterfeit band gaps. Two types of Ba/Ni co-doped (K,Na)NbO3 (KNN) photo-ferroelectric ceramics with relatively wide (~3 ​eV) and narrow (~2 ​eV) band gaps are used to explain the potential problem. This paper hopes to encourage photo-ferroelectric ceramics researchers to use methods other than the optical absorption to determine band gaps in future works.

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Series: Open ceramics
ISSN: 2666-5395
ISSN-L: 2666-5395
Volume: 5
Article number: 100079
DOI: 10.1016/j.oceram.2021.100079
Type of Publication: A1 Journal article – refereed
Field of Science: 216 Materials engineering
Funding: This work was jointly supported by Academy of Finland (grant number 24302332) and University of Oulu. The author acknowledges the Centre for Material Analysis of the University of Oulu for the use of their facilities and for the fabrication of the electrodes.
Copyright information: © 2021 The Author(s). Published by Elsevier Ltd on behalf of European Ceramic Society. This is an open access article under the CC BY license (http://