Controlling nitrogen incorporation in (Eu,Ba,Ca)TiO3-derived perovskite-type oxynitrides through Fermi Level Engineering
Abstract
Defect states directly influence not only functional properties, but also oxynitride formation during ammonolysis. Along with structural stability and charge balance, these defects can cause non-uniform nitrogen incorporation. To address this, the recently proposed Fermi Level Engineering concept provides a powerful alternative of rationalising oxynitride synthesis. By using the electron chemical potential, i.e., the Fermi level, as a unique descriptor, this approach can predict, understand, and manipulate defect formation enthalpies and charge transition levels, subsequently allowing to incorporate defect-property correlations to the concept. This work combines theoretical modelling and experimental characterisation of barium titanium oxynitrides to explain an intrinsic, self-limiting nitridation process. Progressive nitrogen incorporation causes a Fermi level downward shift, leaving further nitrogen substitution on oxygen sites energetically unfavourable, up to 0.03 N per unit formula. We demonstrate that A-site cation substitution in Eu1−xBaxTiO3- and Eu1−xCaxTiO3-derived oxynitrides can be applied to control compensation of the additional negative charge from N3− and keep the Fermi level high. The Eu2+/3+ redox couple enables substitution of oxygen by nitrogen through pinning of the Fermi level at the europium charge transition level, at ∼ 2.9 eV above the VBM. This allows for higher nitrogen uptake of up to 0.65 per formula unit (taken from hot gas extraction) through a more controlled process. Further incorporation is then limited by an intra-Ti(O,N)6 octahedra distortion due to internal bond-angle variance. These findings demonstrate that Fermi Level Engineering provides a pathway to predict and overcome intrinsic synthetic and thermodynamic limitations in oxynitride synthesis.
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BibTeX
@misc{barroso2026controlling,
title = {{Controlling nitrogen incorporation in (Eu,Ba,Ca)TiO$_3$-derived perovskite-type oxynitrides through Fermi Level Engineering}},
author = {Margarida Barroso and Marie Neumann and Rachele Sciotto and Shama Perween and Magdalena O. Cichocka and Jefferson Bettini and Adrián López Vergara and Patrick Zeller and Gaurav Anand and Verena Streibel and Barbara A. J. Lechner and Melanie Appelmann and Oliver Clemens and Ute Kolb and Jan P. Hofmann and Karsten Albe and Andreas Klein and Marc Widenmeyer and Anke Weidenkaff},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.04745},
eprint = {2611.04745},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.04745},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Controlling nitrogen incorporation in (Eu,Ba,Ca)TiO_3-derived perovskite-type oxynitrides through Fermi Level Engineering
AU - Margarida Barroso
AU - Marie Neumann
AU - Rachele Sciotto
AU - Shama Perween
AU - Magdalena O. Cichocka
AU - Jefferson Bettini
AU - Adrián López Vergara
AU - Patrick Zeller
AU - Gaurav Anand
AU - Verena Streibel
AU - Barbara A. J. Lechner
AU - Melanie Appelmann
AU - Oliver Clemens
AU - Ute Kolb
AU - Jan P. Hofmann
AU - Karsten Albe
AU - Andreas Klein
AU - Marc Widenmeyer
AU - Anke Weidenkaff
PY - 2026
DA - 2026/11/03
PB - arXiv
DO - 10.48550/arxiv.2611.04745
UR - https://arxiv.org/abs/2611.04745
AB - Defect states directly influence not only functional properties, but also oxynitride formation during ammonolysis. Along with structural stability and charge balance, these defects can cause non-uniform nitrogen incorporation. To address this, the recently proposed Fermi Level Engineering concept provides a powerful alternative of rationalising oxynitride synthesis. By using the electron chemical potential, i.e., the Fermi level, as a unique descriptor, this approach can predict, understand, and manipulate defect formation enthalpies and charge transition levels, subsequently allowing to incorporate defect-property correlations to the concept. This work combines theoretical modelling and experimental characterisation of barium titanium oxynitrides to explain an intrinsic, self-limiting nitridation process. Progressive nitrogen incorporation causes a Fermi level downward shift, leaving further nitrogen substitution on oxygen sites energetically unfavourable, up to 0.03 N per unit formula. We demonstrate that A-site cation substitution in Eu_1−xBa_xTiO_3- and Eu_1−xCa_xTiO_3-derived oxynitrides can be applied to control compensation of the additional negative charge from N^3− and keep the Fermi level high. The Eu^2+/3+ redox couple enables substitution of oxygen by nitrogen through pinning of the Fermi level at the europium charge transition level, at ∼ 2.9 eV above the VBM. This allows for higher nitrogen uptake of up to 0.65 per formula unit (taken from hot gas extraction) through a more controlled process. Further incorporation is then limited by an intra-Ti(O,N)_6 octahedra distortion due to internal bond-angle variance. These findings demonstrate that Fermi Level Engineering provides a pathway to predict and overcome intrinsic synthetic and thermodynamic limitations in oxynitride synthesis.
ER -