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Conduction mechanisms and complex impedance analysis in La0.6Sr0.4FeO3 ceramic

Authors:
R. Lataoui at University of Sfax
R. Lataoui
A. Triki at University of Sfax
A. Triki
S. Hcini at Université de Kairouan
S. Hcini
Abderrazek Oueslati at University of Sfax
Abderrazek Oueslati
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Abstract and Figures

La0.6Sr0.4FeO3 ceramic was elaborated by solid-state route. Preliminary room-temperature structural analysis evidences the sample formation in the orthorhombic structure and its phase purity. Electrical properties of the studied ceramic have been investigated according to dielectric measurements in the frequency range 10–1 - 10⁶ Hz and the temperature range 93 - 313 K. Electrical conductivity curves exhibit a step-like behavior, at low temperatures, attributed to grain boundaries and grain contributions which are well described by the two Jonscher equations. The grains conduction mechanism is consistent with the thermally activated hopping of small polaron (SPH). Whereas, this mechanism is no longer satisfied for grain boundaries conduction mechanism at lower temperatures. Indeed, this latter is governed by the variable range hopping (VRH) model. This electrical conductivity analysis is further confirmed by the complex impedance formalism according to the obtained activation energies. Analysis of Nyquist plots at low temperatures has evidenced the presence of two grain boundaries effects attributed to the heterogeneous structure of La0.6Sr0.4FeO3 grain boundary according to the morphological analysis. Such characteristic may be at the origin of the grain boundaries electrical conductivity mechanism change at low temperatures.
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Vol.:(0123456789)
1 3
Journal of Electroceramics (2023) 50:121–138
https://doi.org/10.1007/s10832-023-00310-4
Conduction mechanisms andcomplex impedance analysis
in La0.6Sr0.4FeO3 ceramic
R.Lataoui1,2· A.Triki1 · S.Hcini3· A.Oueslati4· S.Zemni2· O.Kanoun5
Received: 24 December 2022 / Accepted: 2 April 2023 / Published online: 28 April 2023
© The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2023
Abstract
La0.6Sr0.4FeO3 ceramic was elaborated by solid-state route. Preliminary room-temperature structural analysis evidences the
sample formation in the orthorhombic structure and its phase purity. Electrical properties of the studied ceramic have been
investigated according to dielectric measurements in the frequency range 10–1 - 106 Hz and the temperature range 93 - 313
K. Electrical conductivity curves exhibit a step-like behavior, at low temperatures, attributed to grain boundaries and grain
contributions which are well described by the two Jonscher equations. The grains conduction mechanism is consistent with
the thermally activated hopping of small polaron (SPH). Whereas, this mechanism is no longer satisfied for grain boundaries
conduction mechanism at lower temperatures. Indeed, this latter is governed by the variable range hopping (VRH) model.
This electrical conductivity analysis is further confirmed by the complex impedance formalism according to the obtained
activation energies. Analysis of Nyquist plots at low temperatures has evidenced the presence of two grain boundaries effects
attributed to the heterogeneous structure of La0.6Sr0.4FeO3 grain boundary according to the morphological analysis. Such
characteristic may be at the origin of the grain boundaries electrical conductivity mechanism change at low temperatures.
Keywords Dielectric measurements· La0.6Sr0.4FeO3 ceramic· Complex impedance analysis· Morphological analysis·
Electrical conductivity analysis
1 Introduction
LaFeO3-based oxides is the most investigated perovskite
materials [1–4] owing to its unique physical properties and
its potential applications [5–10]. Substitution of divalent or
trivalent ions into the La and/or Fe sub-lattices allows tailor-
ing interesting properties of electrical materials for specific
applications such as catalysts, gaz sensors and fuel cells
[11–19]. The replacement of La3+ by Sr2+ leads to a mixed
valence of the Fe3+ and Fe+4 ions [20] which enhances
the electronic conductivity of the mixed valence oxides
La1-xSrxFeO3 [21, 22]. Transport properties of these mate-
rials at low temperatures are mainly governed by thermally
activated hopping process of small polarons of ligand holes
[23] which character changes as function of Sr composition
[24]. Indeed, for low Sr composition, ligand hole character
is primarily made up of O 2p weight and it changes to Fe
3d-O 2p as Sr content increases. This character transition is
confirmed according to dielectric analysis and may be at the
origin of conductivity deviation from linear behavior, given
by the thermally activated hopping process of small polaron
model, at lower temperatures despite its enhancement [23].
Such result has been attributed to carrier nature change i.e.,
the transfer from primary O 2p character to mixed Fe 3d-O
2p for intermediary Sr contents of Lal-xSrxFeO3 ceramics.
Analysis of conduction mechanism at low temperatures
of some ceramics has shown that conduction is governed by
the grain boundaries effect and it is in agreement with the
* A. Triki
trikilamacop@yahoo.fr
1 Laboratoire Des Matériaux Composites, Céramiques et
Polymères, Faculté Des Sciences de Sfax, Université de
Sfax, BP 3018, Sfax, Tunisia
2 Laboratoire de Physico-Chimie Des Matériaux, Département
de Physique, Faculté Des Sciences de Monastir, Université de
Monastir, 5019Monastir, Tunisia
3 Unité de Recherche Valorisation et Optimisation de
l’Exploitation Des Ressources, Faculté des Sciences
et Techniques de Sidi Bouzid, Université de Kairouan,
9100SidiBouzid, Tunisia
4 Laboratoire de Spectroscopies et Caractérisations Optiques
des Matériaux, Faculté Des Sciences de Sfax, Université de
Sfax, BP 3018, Sfax, Tunisia
5 Professorship ofMeasurement andSensor Technology,
Chemnitz University ofTechnology, 09111Chemnitz,
Germany
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