University of Oulu

Shafir, O., Bai, Y., Juuti, J., & Grinberg, I. (2020). Visible-Light-Absorbing Potassium Niobate-Titanate-Molybdate Ferroelectrics. Physical Review Applied, 14(4).

Visible-light-absorbing potassium Niobate-Titanate-Molybdate ferroelectrics

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Author: Shafir, Or1; Bai, Yang2; Juuti, Jari2;
Organizations: 1Department of Chemistry, Bar-Ilan University, Ramat Gan 529002, Israel
2Microelectronics 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, 2.6 MB)
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Language: English
Published: American Physical Society, 2020
Publish Date: 2020-11-03


The interactions of ferroelectric (FE) perovskite oxides (ABO₃) with light are increasingly being studied for different applications, such as photovoltaics and optoelectronics. The combination of different cations at the A and B sites to form solid solutions allows tuning of the material’s properties and, most importantly, the band gap (Eg), which sets the wavelength range of light absorption. Classic FE perovskite oxides, such as BaTiO₃, KNbO₃, and PbTiO₃, exhibit Eg > 3 eV, which limits their implementation in visible-light-absorbing devices. Furthermore, the tuning of their Eg via a solid solution strategy to a lower Eg range is limited by the requirement for the presence of a d⁰ metal at the B site, which is necessary for the FE distortion, but leads to a larger Eg. This gives rise to the challenge of decreasing Eg, while maintaining FE distortion. Here, we use first-principles calculations to explore the FE and optical properties of the (KNbO3)x(KTi1/2Mo1/2O3)1−x(KNTM) perovskite oxide solid solution. The introduction of Ti⁴⁺ and Mo⁶⁺ into the parent KNbO₃ decreases the Eg to about 2.2 eV for x = 0.9, while preserving or enhancing polarization. Experimental fabrication and characterization show that the obtained KNTM material at x = 0.9 has an orthorhombic structure at room temperature and a direct gap of <2.2 eV, confirming first-principles-based predictions. These properties make KNTM a promising candidate for further studies and applications as a visible-light-absorbing FE material.

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Series: Physical review applied
ISSN: 2331-7019
ISSN-E: 2331-7019
ISSN-L: 2331-7019
Volume: 14
Issue: 4
Article number: 044052
DOI: 10.1103/PhysRevApplied.14.044052
Type of Publication: A1 Journal article – refereed
Field of Science: 216 Materials engineering
Funding: O.S. and I.G. acknowledge support by the US-Israel Binational Science Foundation (Grant No. 2016637). Y.B. would like to acknowledge joint funding by the University of Oulu and the Academy of Finland profiling action ‘‘Ubiquitous wireless sensor systems’’ (Grant No. 24302332). The authors also acknowledge the Centre for Material Analysis of the University of Oulu for the use of their facilities.
Copyright information: © 2020 American Physical Society. The Definitive Version of Record can be found online at