arXiv subjects

M. El Marssi

Publications and source records attributed to M. El Marssi.

At least 19 recordsLinked to original sources

arXiv2025

Lithium doping's effects on the microstructural,dielectric,energy storage,optical and electrical properties of BaTi0.89Sn0.11O3 ceramics

This research study the sol/gel synthesis of lithium-doped barium stannate titanate BaTi0.89Sn0.11O3 (BTS11) and investigates how varying composition with lithium affect its structural, morphological, ferroelectric, optical, and electrical properties. The phase of the sol/gel prepared samples with different compositions BaLixTi0.89Sn0.11O3 (BLxTS11), where x = 0%, 2%, 4%, 6%, 8, and 10%, was examined using X-ray diffraction (XRD), which showed the development of a pure perovskite structure. Furthermore, structural characterization was performed with Raman spectroscopy to identify changes in structure and chemical environment resulting from Li incorporation. The doping caused changes in the morphology and grain size of BLxTS11 pellets, as examined through SEM micrographs. These micrographs showed clear alterations in grain size that were inversely related to the lattice strain of BLxTS11. The samples were subsequently examined for their ferroelectric properties. All samples exhibited their maximum dielectric constant at approximately 45-50 °C. Furthermore, relationships between the chemical, structural, and morphological characteristics of the BLxTS11 ceramics and their energy storage capabilities were identified. Based on the P-E hysteresis behavior, the BL6TS11 ceramic (x=6%) ferroelectric exhibited superior energy-storage capabilities, featuring a recoverable energy-storage density of 225 mJ/cm3 and an energy-storage efficiency of 60%. An examination of the material's optical and electrical properties revealed that Li doping led to a reduction in the band gap values and a considerable increase in resistivity.

cond-mat.mtrl-sci↗

arXiv2024

Dielectric and energy-storage properties of Ba0.85Ca0.15Zr0.10Ti0.90O3 ceramics with BaO-Na2O-Nb2O5-WO3-P2O5 glass addition

Lead-free Ba0.85Ca0.15Zr0.10Ti0.90O3 (BCZT) ceramics with different BaO-Na2O-Nb2O5-WO3-P2O5 (BNNWP) glass content, forming (1-x)BCZT-xBNNWP lead-free ceramics (abbreviated as BCZTx; x=0, 2, 4, 6, and 8wt%) were synthesized using the conventional solid-state processing route. The XRD investigation shows the coexistence of tetragonal and orthorhombic phases in BCZT pure. Likewise, only the tetragonal phase was detected in BCZTx (x = 2-8 wt%) ceramics. The SEM findings indicate that the average grain size decreases as the amount of BNNWP glass additives increases. In addition, BCZT ceramics Amodified with glass additions showed narrower hysteresis loops and a large electric field. The BCZT4 showed the highest recovered energy density of 0.52 J/cm3 at 135kV/cm with an energy storage efficiency of 62.4%, which is increased by 6.6 compared to BCZT0 (0.075 J/cm3). The energy density was also calculated using the Landau-Ginzburg-Devonshire (LGD) theory

physics.app-ph↗

arXiv2021

Structural behaviour of BiFeO3/SrRuO3 superlattices: an X-ray diffraction and Raman spectroscopy investigation

Epitaxial BiFeO3/SrRuO3 superlattices have been grown by pulsed laser deposition on a (001) oriented LaAlO3 substrate and probed by X-ray diffraction and Raman spectroscopy. To investigate the structural competition between rhombohedral BiFeO3 and orthorhombic SrRuO3 the total thickness of all SLs was kept constant and the bilayer thickness (period) Λ was varied. The interlayer strain effects are therefore tuned from large strain effects (short Λ period) to quasi-relaxed structure (large Λ). A complementary investigation using X-ray diffraction and phonon dynamics hints to change from a rhombohedral to a tetragonal structure in the superlattices with the increase of the interlayer strain effect.

cond-mat.mtrl-sci↗

arXiv2021

Impedance spectroscopy and conduction mechanism of a BiFe$_{0.95}$Mn$_{0.05}$O$_3$ thin film

Dielectric response and conduction mechanism were investigated for a multiferroic BiFe$_{0.95}$Mn$_{0.05}$O$_3$ epitaxial thin film. A contribution from a thermally activated interface (0.37 eV) and the bulk of the film on the dielectric response were observed through the comparison between experimental results and equivalent circuit model. The low frequency interface relaxation signatures strongly suggest a Maxwell-Wagner space charge origin. The alternative current conductivity deduced from the model follows a power law frequency dependence suggesting a polaronic hopping mechanism while the low frequency limit is in perfect agreement with the direct current conduction mechanism. The current-voltage characteristics were indeed correlated with Schottky-Simmons interface limited transport with activation energy of 0.36 eV, close to the one extracted from the impedance analysis. Such analysis of the electrostatic landscape and dielectric behaviour may help to further understanding the anomalous photo-induced properties in the BiFeO$_3$ system.

cond-mat.mtrl-sci↗

arXiv2020

Enhancing the dielectric, electrocaloric and energy storage properties of lead-free Ba0.85Ca0.15Zr0.1Ti0.9O3 ceramics prepared via sol-gel process

The Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) ceramics were successfully prepared by sol-gel process, and sintered at 1420 degree. The effect of sintering times (2, 4 and 6 h) on structural, microstructural, electric properties, energy storage, and electrocaloric effect was systematically examined. X-ray diffraction (XRD) results show that all the samples crystallize in the pure perovskite structure. The morphotropic phase transition from the tetragonal to the orthorhombic phase (T-O) was identified and confirmed by Rietveld refinement. The BCZT ceramic sintered at 1420 degree for 4h possesses a good relative density of 98%, and exhibits optimal properties with a high dielectric permittivity ~16310, a large electrocaloric effect coefficient ~ 0.244Kmm/kV and an energy density storage of ~ 10.61 mJ/cm3.

cond-mat.mtrl-sci↗

arXiv2020

The electrocaloric response in Lanthanum-modified lead zirconate titanate ceramic

Over the past decades, there has been significant interest in new cooling technology based on the electrocaloric effect. The large electrocaloric effect observed in polymeric and inorganic ferroelectric materials made possible development of dielectric cooling devices of a new generation. We report a significant impact of annealing on the electrocaloric effect observed in 12/65/35 PLZT bulk ceramics. The electrocaloric data were obtained by direct measurements. Electrocaloric results confirm the existence of the significant electrocaloric response in this relaxor ferroelectric PLZT composition exceeding previously obtained electrocaloric values in perovskite relaxor ferroelectrics such as PMN-PT and x/65/35 PLZT ceramics.

cond-mat.mtrl-sci↗

arXiv2020

Tailoring the photovoltaic effect in (111) oriented BiFeO3/LaFeO3 superlattices

Ferroelectric and photovoltaic properties of BiFeO3/LaFeO3 superlattices grown by pulsed laser deposition have been investigated being the bilayer thickness). For a high concentration of BiFeO3 a ferroelectric state is observed simultaneously with a switchable photovoltaic response. In contrast for certain concentration of LaFeO3 a non-switchable photovoltaic effect is evidenced. Such modulation of the PV response in the superlattices is attributed to the ferroelectric to paraelectric phase transition which is controlled with the increase of x. Remarkably, concomitant to this change of PV mechanism, a change of the conduction mechanism also seems to take place from a bulk-limited to an interface-limited transport as x increases.

cond-mat.mtrl-sci↗

arXiv2020

Quantification and Mapping of Elastic Strains Ferroelectric BaZrO3/BaTiO3 Superlattices

We report on quantification and elastic strain mapping in two artificial BaZrO3/BaTiO3 (BZ/BT) superlattices having periods of 6.6 nm and 11 nm respectively, grown on (001) SrTiO3 single crystal substrate by pulsed laser deposition technique. The methodology consists of a combination of high-resolution scanning transmission electron microscopy and nanobeam electron diffraction associated with dedicated algorithm for diffraction patterns processing originally developed for semiconductors to record the strains at atomic scale. Both in-plane and out-of-plane elastic strains were then determined at 2 nm spatial resolution and their average values were used to map the strains along and transverse to the epitaxial growth direction of both samples to determine its variation along several BZ/BT interfaces. In addition, the variation of the width of the inter-diffusion BT/BZ interfaces and intermixing between different layers are estimated. The obtained width average value measured in these inter-diffusion interfaces vary from 8 to 12% and from 9 to 11% for both superlattices having period of 6.6 nm and 11 nm respectively. These inter-diffusion interfaces and the inherent elastic strains due to the confined layers of the superlattices are known to be the most important parameters, responsible of the change in their functional properties.

cond-mat.mtrl-sci↗

arXiv2020

Structural, dielectric and magnetic studies of (0-3) type multiferroic (1-x) BaTi0.8Sn0.2O3-(x) La0.5Ca0.5MnO3 (0 <x< 1) composite ceramics

Multiferroic composites with the composition (1-x) BaTi0.8Sn0.2O3 - (x) La0.5Ca0.5MnO3 (x =0, 0.3, 0.5, 0.7, 0.9 and 1) were prepared by sol-gel techniques. Rietveld refinements of the composites with 0-3 and 3-0 type connectivities exhibit the formation of pure phases and confirm the fraction of the composite samples. It was found that the composites grain size decreases slightly with increasing the La0.5Ca0.5MnO3 content. Magnetic measurements of the composite ceramics exhibit a gradual increase in saturation and remanent magnetization with increasing La0.5Ca0.5MnO3 content. Dielectric data demonstrate that the composite materials show high values of the dielectric constant in comparison with the parent compound BaTi0.8Sn0.2O3 (BTSO). In addition, an attempt is made to measure the magnetoelectric coupling coefficient and to explain the negative permittivity and losses occurring in these materials at a certain frequency and temperature conditions.

cond-mat.mtrl-sci↗

arXiv2020

Structural, dielectric, ferroelectric and tuning properties of Pb-free ferroelectric Ba0.9Sr0.1Ti1-xSnxO3

A series of Pb-free ferroelectric materials Ba0.9Sr0.1Ti1-xSnxO3 (BSTS-x) with 0 < x < 0.15 was successfully prepared via solid-state reaction method. The effect of Sn substitution on the crystal structure, microstructure, dielectric behavior, ferroelectric and tunable features of BSTS-x ceramics were systematically investigated. Room temperature (RT) x-ray diffraction (XRD) analysis using the Rietveld refinement method reveals that all the synthesized BSTS-x ceramics were well crystallized into single perovskite structure. The results show a tetragonal phase for 0.00 < x < 0.02, which evolves to orthorhombic and tetragonal coexisting phases for 0.05 < x < 0.07. The composition x = 0.10 showed a mixture of tetragonal, orthorhombic and rhombohedral phases at RT, while a single cubic phase is observed for x = 0.15. The crystal phases determined by XRD were confirmed by Raman spectroscopy. Enhanced dielectric permittivity with a maximum value of ε'~ 35000 is observed for x = 0.10 at RT. The ferroelectric behavior of BSTS-x ceramics was investigated through polarization hysteresis loops and tunability measurements. High tunability of 63% at RT and under the low DC-applied electric field of 1.40 kV/cm is achieved for x = 0.10.

cond-mat.mtrl-sci↗

arXiv2020

Electrocaloric response in Lanthanum-modified lead zirconate titanate ceramics

Recent findings of a large electrocaloric (EC) effect in polymeric and inorganic ferroelectric materials open a potential possibility of development of solid-state cooling or heating devices of new generation with better energy efficiency that may be less harmful for the environment. We investigate by using direct measurements, the temperature and electric field dependence of the electrocaloric response in Pb1-xLax(ZryTi1-y)1-x/4O3 bulk ceramics (PLZT) with x=0.06 and 0.12. Here, the properties of the EC response were probed in a part of the PLZT composition phase diagram with low y=0.40 composition, in which the EC effect was not previously studied. Measurement results show the existence of the sizeable EC response in 12/40/60 PLZT sample with the EC temperature change (ΔTEC) of 2.92 K at 430 K and 80 kV/cm. This value exceeds previously obtained ΔTEC values in relaxor ferroelectric x/65/35 PLZT compositions and rivaling the best EC response in lead magnesium niobate-lead titanate ceramics. The electrocaloric responsivity (ΔT/ΔE) value of 0.41x10-6 Km/V determined at a lower electric field of 20 kV/cm and 410 K is comparable to those observed in other perovskite ferroelectrics.

cond-mat.mtrl-sci↗

arXiv2019

Chemical synthesis and magnetic properties of monodisperse cobalt ferrite nanoparticles

In this work, a successful synthesis of magnetic cobalt ferrite (CoFe2O4) nanoparticles is presented. The synthesized CoFe2O4 nanoparticles have a spherical shape and highly monodisperse in the selected solvent. The effect of different reaction conditions such as temperature, reaction time and varying capping agents on the phase and morphology is studied. Scanning transmission electron microscopy showed that the size of these nanoparticles can be controlled by varying reaction conditions. Both X-ray diffraction and energy dispersive X-ray spectroscopy corroborate the formation of CoFe2O4 spinel structure with cubic symmetry. Due to optimized reaction parameters, each nanoparticle was shown to be a single magnetic domain with diameter ranges from 6 to 16 nm. Finally, the magnetic investigations showed that the obtained nanoparticles are superparamagnetic with a small coercivity value of about 315 Oe and a saturation magnetization of 58 emu/g at room temperature. These results make the cobalt ferrite nanoparticles promising for advanced magnetic nanodevices and biomagnetic applications.

cond-mat.mtrl-sci↗

arXiv2019

Synthesis of La0.5Ca0.5-x xMnO3 nanocrystalline manganites by sucrose assisted auto combustion route and study of their structural, magnetic and magnetocaloric properties

Perovskite manganite La0.5Ca0.5-x xMnO3 (LCMO) nanomaterials were elaborated using the sucrose modified auto combustion method. Rietveld refinements of the X-ray diffraction patterns of the crystalline structure confirm a single-phase orthorhombic state with Pbnm space group (No. 62). The Ca-vacancies were voluntarily created in the LCMO structure in order to study their influence on the magnetic behaviour in the system. The magnetic susceptibility was found to be highly enhanced in the sample with Ca-vacancies. Paramagnetic-to-ferromagnetic phase transition was evidenced in both samples around 254 K. This transition is, characterized by a drastic jump of the susceptibility in the sample with Ca-vacancies. The maximum of entropy change, observed for both compounds at magnetic field of 6T was 2.30 J kg-1K-1 and 2.70 J kg-1K-1 for the parent compound and the lacunar one respectively. The magnetocaloric adiabatic temperature change value calculated by indirect method was 5.6 K and 5.2 K for the non-lacunar and Ca-vacancy compound, respectively. The Ca-lacunar La0.5Ca0.5-x xMnO3 (x=0.05) reported in this work demonstrated overall enhancement of the magnetocaloric effect over the LCMO. The technique used to elaborate LCMO materials was beneficial to enhance the magnetocaloric effect and magnetic behaviour. Therefore, we conclude that this less costly environmentally friendly system can be considered as more advantageous candidate for magnetic refrigeration applications then the commonly Gd-based compounds.

cond-mat.mtrl-sci↗

arXiv2019

Structural, dielectric and magnetic properties of multiferroic (1-x) La0.5Ca0.5MnO3-(x) BaTi0.8Sn0.2O3 laminated composites

High performance lead-free multiferroic composites are desired to replace the lead-based ceramics in multifunctional devices applications. Laminated compounds were prepared from ferroelectric and ferromagnetic materials. In this work, we present laminated ceramics compound by considering the ferromagnetic La0.5Ca0.5MnO3 (LCMO) and the ferroelectric BaTi0.8Sn0.2O3 (BTSO) in two different proportions. Compounds (1-x) LCMO-(x) BTSO with x=1 and 0 (pure materials) were synthesized by the sol gel method and x=0.7 and 0.5 (laminated) compounds were elaborated by welding appropriate mass ratios of each pure material by using the silver paste technique. Structural, dielectric, ferroelectric, microstructure and magnetic characterization were conducted on these samples. X-ray scattering results showed pure perovskite phases confirming the successful formation of both LCMO and BTSO. SEM images evidenced the laminated structure and good quality of the interfaces. The laminated composite materials have demonstrated a multiferroic behavior characterized by the ferroelectric and the ferromagnetic hysteresis loops. Furthermore, the enhancement of the dielectric constant in the laminated composite samples is mainly attributed to the Maxwell-Wagner polarization.

cond-mat.mtrl-sci↗

arXiv2019

Structural investigation of (111) oriented (BiFeO3)(1-x)Λ/(LaFeO3)xΛ superlattices by X-ray diffraction and Raman spectroscopy

(BiFeO3)(1-x)Λ/(LaFeO3)xΛ superlattices (SLs) with varying x have been grown by pulsed laser deposition on (111) oriented SrTiO3 substrates. In order to obtain good epitaxy and flat samples a conducting SrRuO3 buffer has been deposited prior to the superlattices to screen the polar mismatch for such (111) SrTiO3 orientation. X-ray diffraction reciprocal space mapping on different family of planes were collected and evidenced a room temperature structural change at x=0.5 from a rhombohedral/monoclinic structure for rich BiFeO3 to an orthorhombic symmetry for rich LaFeO3. This symmetry change has been confirmed by Raman spectroscopy and demonstrates the different phase stability compared to similar SLs grown on (100) SrTiO3. The strongly anisotropic strain and oxygen octahedral rotation/tilt system compatibility at the interfaces probably explain the orientation dependence of the phase stability in such superlattices.

cond-mat.mtrl-sci↗

arXiv2018

Dielectric relaxation and predominance of NSPT and OLPT conduction processes in Ba0.9Sr0.1TiO3

We investigate the relaxation and conduction mechanism of Ba0.90Sr0.10TiO3 (BST) ceramic, synthesized by the solid state reaction method. The dielectric and relaxation properties are analyzed in the temperature range of 380-450°C with alternative current in the frequency range of 20Hz-1MHz. Variation of dielectric constant, ε', with temperature shows a normal ferroelectric transition at Tc=95°C with a weak degree of diffuseness. The modified Cole-Cole equation is used to describe all contributions to the relaxation mechanism. The frequency exponent m(ω,T) deduced from experimental data of the dielectric loss (ε") as m(ω, T)=($\partial$ ln ε"/$\partial$ ln ω) shows a temperature and frequency dependence. Two conduction process are observed: non-overlapping small-polaron tunneling (NSPT) at low frequencies and overlapping large polaron tunneling (OLPT) at high frequencies. The analysis of Nyquist plots reveals also the presence of two contributions, who which the activation energies have been calculated.

cond-mat.mtrl-sci↗

arXiv2015

Electrocaloric effect in Ba(0.2)Ca(0.8)Ti(0.95)Ge(0.05)O(3) determined by a new pyroelectric method

The present letter explores the electrocaloric effect (ECE) in the lead free oxide Ba0.8Ca0.2Ti0.95Ge0.05O3 ceramics (BCTG). The electrocaloric responsivity (dT/dE) was determined by two different methods using the Maxwell relationship (dT/dE)~(dP/dT)_E. In a first well-known indirect method, P-E hysteresis loops were measured in a wide temperature range from which the pyroelectric coefficient p_E=(dP/dT)_E and thus (dT/dE) were determined by derivation of P(T,E) data. In the second novel method the pyroelectric coefficient p_E and consequently the electrocaloric responsivity was determined by direct measurements of the pyroelectric currents under different applied electric fields. Within the experimental error good agreement was obtained between two methods with an electrocaloric responsivity equal to 0.18 +/- 0.05 10-6 K.m.V-1 was obtained at about 410 K

cond-mat.mtrl-sci↗

arXiv2010

Electric-field-induced monoclinic phase in (Ba,Sr)TiO$_3$ thin film

We have studied electric-field-induced symmetry lowering in the tetragonal (001)-oriented heteroepitaxial (Ba$_{0.8}$Sr$_{0.2}$)TiO$_3$ thin film deposited on (001)MgO substrate. Polarized micro-Raman spectra were recorded from the film area in between two planar electrodes deposited on the film surface. Presence of \textit{c}-domains with polarization normal to the substrate was confirmed from polarized Raman study under zero field, while splitting and hardening of the \textit{E}(TO) soft mode and polarization changes in the Raman spectra suggest monoclinic symmetry under external electric field.

cond-mat.mtrl-sci↗