Cobalt doping ZnO nanoparticles: from substitutional doping to interstitial expansion for optoelectronic applications
Abstract
The influence of cobalt (Co) doping on the structural and optical properties of ZnO nanoparticles (NPs) synthesized via the sol-gel method was investigated. The obtained nanopowder was calcined at 400 °C for 2 h in a muffle furnace. X-ray diffraction (XRD) patterns were analyzed using the Rietveld refinement method, confirming a hexagonal wurtzite ZnO structure (space group P6 3 mc) with no secondary phases.
With increasing nominal Co content, the XRD peaks shifted progressively toward higher diffraction angles, indicating the successful substitution of Co ions at Zn sites within the ZnO lattice. As the Co concentration increased up to 3%, both lattice parameters (a and c) decreased, whereas at 5% Co, an opposite trend occurred and a slight lattice expansion was observed, which suggests additional interstitial incorporation of Co 2+ ions. The crystallite size and lattice strain were evaluated using the Williamson-Hall method coupled with Rietveld refinement. These structural observations were corroborated by scanning electron microscopy (SEM) analyses, which revealed the morphology and grain homogeneity of the samples. Fourier-transform infrared (FTIR) spectra confirmed the formation of a pure wurtzite ZnO phase, showing the characteristic Zn-O stretching vibrations. Optical characterization revealed a non-monotonic evolution of the optical band gap with Co content (decrease up to 3%, followed by a partial increase at 5%), consistent with the photoluminescence (PL) measurements pattern. The electron paramagnetic resonance (EPR) spectra reveal signals attributed to intrinsic point defects together with paramagnetic Co 2+ in tetrahedral environments and Co 3+ in interstitial octahedral environments, with evidence suggestive of exchange coupling (to be confirmed by direct magnetic measurements).
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BibTeX
@article{khlifi2026cobalt,
title = {{Cobalt doping ZnO nanoparticles: from substitutional doping to interstitial expansion for optoelectronic applications}},
author = {Najet Khlifi and Mohamed Nafti Bessadok and Nejib Ihzaz and Olivier Toulemonde and Arnaud Dandre and Christine Labrugère-Sarroste and Lassaad El Mir},
journal = {RSC Advances},
year = {2026},
month = oct,
doi = {10.1039/d6ra03712g},
url = {https://u-bordeaux.hal.science/hal-05835101v1},
note = {CC BY-NC 4.0},
}
RIS
TY - JOUR
TI - Cobalt doping ZnO nanoparticles: from substitutional doping to interstitial expansion for optoelectronic applications
AU - Najet Khlifi
AU - Mohamed Nafti Bessadok
AU - Nejib Ihzaz
AU - Olivier Toulemonde
AU - Arnaud Dandre
AU - Christine Labrugère-Sarroste
AU - Lassaad El Mir
PY - 2026
DA - 2026/10/22
JO - RSC Advances
DO - 10.1039/d6ra03712g
UR - https://u-bordeaux.hal.science/hal-05835101v1
AB - The influence of cobalt (Co) doping on the structural and optical properties of ZnO nanoparticles (NPs) synthesized via the sol-gel method was investigated. The obtained nanopowder was calcined at 400 °C for 2 h in a muffle furnace. X-ray diffraction (XRD) patterns were analyzed using the Rietveld refinement method, confirming a hexagonal wurtzite ZnO structure (space group P6 3 mc) with no secondary phases. With increasing nominal Co content, the XRD peaks shifted progressively toward higher diffraction angles, indicating the successful substitution of Co ions at Zn sites within the ZnO lattice. As the Co concentration increased up to 3%, both lattice parameters (a and c) decreased, whereas at 5% Co, an opposite trend occurred and a slight lattice expansion was observed, which suggests additional interstitial incorporation of Co 2+ ions. The crystallite size and lattice strain were evaluated using the Williamson-Hall method coupled with Rietveld refinement. These structural observations were corroborated by scanning electron microscopy (SEM) analyses, which revealed the morphology and grain homogeneity of the samples. Fourier-transform infrared (FTIR) spectra confirmed the formation of a pure wurtzite ZnO phase, showing the characteristic Zn-O stretching vibrations. Optical characterization revealed a non-monotonic evolution of the optical band gap with Co content (decrease up to 3%, followed by a partial increase at 5%), consistent with the photoluminescence (PL) measurements pattern. The electron paramagnetic resonance (EPR) spectra reveal signals attributed to intrinsic point defects together with paramagnetic Co 2+ in tetrahedral environments and Co 3+ in interstitial octahedral environments, with evidence suggestive of exchange coupling (to be confirmed by direct magnetic measurements).
SN - 2046-2069
ER -