Okatan, Mahmut Barış
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Barış Okatan, Mahmut
Okatan, B.
Okatan, Mahmut B.
Okatan, Mahmut Baris
Okatan, M. B.
Okatan, MB
Okatan, M. Bans
Okatan, M. Barış
Baris Okatan, M.
Baris Okatan, Mahmut
Barış Okatan, M.
Okatan, M. Baris
Okatan, B.
Okatan, Mahmut B.
Okatan, Mahmut Baris
Okatan, M. B.
Okatan, MB
Okatan, M. Bans
Okatan, M. Barış
Baris Okatan, M.
Baris Okatan, Mahmut
Barış Okatan, M.
Okatan, M. Baris
Job Title
Email Address
barisokatan@iyte.edu.tr
Main Affiliation
03.09. Department of Materials Science and Engineering
Status
Current Staff
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Turkish CoHE Profile ID
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WoS Researcher ID
Sustainable Development Goals
SDG data is not available
Documents
57
Citations
1732
h-index
26
Documents
56
Citations
1708
Scholarly Output
10
Articles
9
Views / Downloads
5278/1271
Supervised MSc Theses
0
Supervised PhD Theses
0
WoS Citation Count
54
Scopus Citation Count
57
Patents
0
Projects
0
WoS Citations per Publication
5.40
Scopus Citations per Publication
5.70
Open Access Source
2
Supervised Theses
0
| Journal | Count |
|---|---|
| Journal of Applied Physics | 2 |
| Acta Materialia | 1 |
| Annalen der Physik | 1 |
| Encyclopedia of Materials: Electronics | 1 |
| Ferroelectrics | 1 |
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10 results
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Now showing 1 - 10 of 10
Book Part Citation - Scopus: 1Electrocaloric Ceramics(Elsevier, 2023) Alkoy, S.; Okatan, M.B.; Mısırlıoğlu, I.B.; Menşur-Alkoy, E.Electrocaloric effect (ECE) is a coupling between thermal and electrical phenomena, specifically it is the change in the entropy of a dielectric material as a result of an electrical stimulus. Electrocaloric materials are currently being investigated as a solid state refrigeration approach for on-chip cooling applications. Among the organic and inorganic electrocaloric material choices, electrocaloric ceramics are at the forefront with their higher electrocaloric coefficients. This article gives a background on the fundamentals of electrocalorics and then discusses the general trends in the literature on the electrocaloric ceramics research. © 2023 Elsevier Inc. All rights reservedArticle Citation - WoS: 14Citation - Scopus: 13Effect of Texture on the Electrical and Electrocaloric Properties of 0.90pb(mg1/3nb2 Relaxor Ceramics(American Institute of Physics, 2020) Mensur Alkoy, Ebru; Okatan, M. Barış; Aydın, Ecem; Kılıç, Yusuf; Mısırlıoğlu, I. Burç; Alkoy, SedatFunctional properties of ferroelectric compositions depend strongly on the type of stable crystalline phase at a given temperature and texturing. In addition to defining a governing crystallographic axis among the grains with respect to a global reference axis, texturing in these systems is also often meant to imply the relationship between an external applied field and the polar axis. Here, we synthesize randomly oriented and 001(pc) textured 0.90Pb(Mg1/3Nb2/3)O-3-0.10PbTiO(3) solid solutions that fall into the relaxor category. A >95% degree of 001(pc) texturing was achieved by the use of single crystal BaTiO3 template crystallites whose volume fraction does not exceed 5% of the entire sample volume. Electrical measurements made on random and textured samples reveal the impact of texture on the hysteresis and the dielectric response. A Curie-Weiss analysis of the temperature dependent dielectric data shows the degree of relaxor behavior in random and textured samples. As similar compositions have recently been getting interest for electrothermal management applications, we compute the electrocaloric (EC) response of the random and textured samples using indirect methods followed by an estimation of the EC response with a subsequent thermodynamic analysis to shed light on the effect of texture on the observed differences between the textured and the random oriented samples. We finally compare and contrast on the desirability of texturing in these systems for use as EC components for thermal management applications.Article Citation - WoS: 3Citation - Scopus: 5Temperature Dependent Electrical and Electrocaloric Properties of Textured 0.72pmn-0.28pt Ceramics*(Taylor & Francis, 2021) Böbrek, İrem; Berksoy Yavuz, Ayşe; Kaya, M. Yunus; Alkoy, Sedat; Okatan, Mahmut Barış; Mısırlıoğlu, İbrahim Burç; Mensur Alkoy, EbruLead magnesium niobate (PMN) - lead titanate (PT) solid solution ceramics in the ratio of 0.72PMN-0.28PT was produced by a combination of tape-casting in ⟨001⟩(pc) textured and random forms. The Lotgering factor, f, of textured ceramics was approximately calculated as 80%. Modified Curie-Weiss analysis indicated relaxor dominant behavior for both the random and textured ceramics. Development of texture led to an enhancement in the electromechanical properties with converse piezoelectric charge coefficient (d(33)*) under 20 kV/cm electric field reaching 545 pm/V for the textured ceramic. Electrocaloric (EC) behavior of random and textured ceramics were obtained from indirect measurements using temperature dependent polarization vs. electric field hysteresis loops. An EC temperature change (Delta T-EC) of similar to 0.5 K was calculated from the PMN-28PT ceramics at around 80 degrees C under an electric field of 60 kV/cm. Development of texture was demonstrated to have led to an anisotropy in the EC response.Article Citation - WoS: 6Citation - Scopus: 6Effect of the Synthesis Method and Particle Size on Bczt Electrocaloric Properties(Pergamon-elsevier Science Ltd, 2025) Temel, Helin; Avci, Tubanur; Okatan, M. Baris; Alkoy, Sedat; Misirlioglu, I. Burc; Mensur, EbruIn this study, the electrocaloric properties of BCZT ceramics fabricated through different processing methods: solid-state and sol-gel were investigated. The calcination process was done for BCZT powders obtained by sol-gel process at 900 degrees C for 2 h and by solid-state calcination method at 1200 degrees C for 6 h. BCZT-SG ceramics exhibited higher Delta T values, particularly at lower temperatures (similar to 0 degrees C-20 degrees C), and a stronger response to the electric field, suggesting a more efficient domain structure due to sol-gel processing. Notably, BCZT-SGH samples demonstrated the most complex and pronounced electrocaloric behavior, with dual Delta T peaks around 0 degrees C and 50 degrees C, and the highest Delta T of 2.5 K at 80 kV/cm and 50 degrees C, surpassing values in the literature. Especially, high Delta T results at 0 degrees C allows using this material in the extreme conditions. These results emphasize the significant role of processing techniques in tailoring the structural, dielectric, and electrocaloric properties of BCZT ceramics for high-performance energy applications.Article Citation - WoS: 13Citation - Scopus: 14Landau, Ginzburg, Devonshire and Others(Taylor & Francis, 2020) Levanyuk, Arkady P.; Mısırlıoğlu, İbrahim Burç; Barış Okatan, MahmutMacroscopic modeling of ferroelectric properties refers usually to Landau-Ginzburg-Devonshire theory. This paper questions the meaningfulness of this term, discussing contributions of the three authors in the title to what is supposed to be a theory. The limitations of every contribution are analysed. In the main text and, to more extent in the Supplementary Material, the Landau theory is presented from an unusual perspective starting from simple mechanical models of spontaneous symmetry breaking and finishing by the Ising model. The aim of the presentation is to emphasize along with the qualitative breakthroughs the approximate character of macroscopic modeling associated with the above three authors. © 2020 Taylor & Francis Group, LLC.Article Citation - WoS: 6Citation - Scopus: 6Weak Dependence of Voltage Amplification in a Semiconductor Channel on Strain State and Thickness of a Multidomain Ferroelectric in a Bilayer Gate(American Chemical Society, 2023) Misirlioglu, I.B.; Yapici, M.K.; Sendur, K.; Okatan, M.B.Ferroelectric/dielectric layered stacks are of special interest as gate oxides in the pursuit of designing low-power transistors, where the electrostatics of such stacks are thought to provide a means to allow for voltage amplification in the semiconductor channel. Strain and thickness dependence of the response of such a gate stack in relation to voltage amplification in a semiconductor channel becomes important to identify, which is what we study in this work using a thermodynamic approach. For a ferroelectric multidomain state as the stable phase in the stack, our findings show that a limited magnitude of voltage amplification appears to be feasible. Voltage amplification at the semiconductor surface is computed to hardly exceed 1.2 in thick bilayers (40 nm) for strains stabilizing the multidomain state and attains even less than this value for the thinner stacks. © 2023 American Chemical Society.Article Citation - WoS: 3Citation - Scopus: 4Enhancement of the Electrocaloric Effect in Pbzr0.7ti0.3o3 Ceramics Via La Doping: Driven by Phase Co-Existence or Defect Effects?(Elsevier, 2022) Gözüaçık, Namık Kemal; Bayır, Mustafa Çağrı; Okatan, Mahmut Barış; Mısırlıoğlu, I. Burç; Alkoy, Sedat; Menşur Alkoy, EbruLattice defects and their effects have been pivotal in studies of phase transitions in a wide range of materials. Introduction of such defects into a ferroelectric material through doping of secondary elements can be tailored towards specific applications but the mechanism through which the bulk properties change is seldom scrutinized. Here we study the effect of systematic La substitution into PbZr0.7Ti0.3O3 (PZT 70/30) ceramics whereby we analyzed the temperature dependent properties and estimated the temperature changes that could be induced upon application of an external electric field, namely the electrocaloric effect (ECE). Expecting the entropic changes to be maximal under an applied field, the suitability of the La doped PZT 70/30 system for EC applications had been a motivation to undertake the current task as this composition reportedly can host a rich variety of phases depending on La content including relaxor and antiferroelectric (AFE) states. An electrocaloric (EC) temperature change of 1.15 °C in a wide range of temperatures for 8% La doping at 45 kV/cm applied field was estimated from experimental data, the possible origins of which is discussed. We were able to explain the experimental results by adopting a Landau-Ginzburg based computational approach coupled with elasticity and electrostatics whereby La sites are treated as point defects in a PZT 70/30 lattice. The gradual slanting of the hystereses and reduction of the transition temperature in the samples with increasing La content is claimed to be a direct consequence of the electrical fields due to formation of dipolar defect complexes as backed by our simulations. The ECE is discussed in the light of the simulations and recent results for AFE ceramics.Article Citation - WoS: 3Citation - Scopus: 2Effects of Interphase Boundaries in Ginzburg-Landau One-Dimensional Model of Two-Phase States in Clamped Systems(American Institute of Physics, 2021) Levanyuk, Arkady P.; Minyukov, Sergey A.; Mısırlıoğlu, İbrahim Burç; Okatan, Mahmut BarışPrevious Landau-type models of two-phase state formation in clamped systems whose material exhibits first-order phase transitions in free state neglects the existence of interphase boundaries. Here, we take them into account in the framework of a Ginzburg-Landau one-dimensional model to study the dependence of characteristics of the two-phase state on system size. Unlike earlier works, we find that the transition to the two-phase state from both the symmetrical and nonsymmetrical phases is not continuous but abrupt. For a one-dimensional system with length L studied in this work, we show that the formation of two-phase state begins with a region whose size is proportional to root L. The latent heat of the transition is also proportional to root L -> infinity, recovering the earlier result for infinite systems. The temperature width of the two-phase region decreases with decreasing of L, but we are unable to answer the question about the critical length for two-phase state formation because the approximation used in analytical calculations is valid for sufficiently large L. A region of small values of L was studied partially to reveal the limits of validity of the analytical calculations. The main physical results are also obtainable within a simple approximation that considers the energy of interphase boundary as a fixed value, neglecting its temperature dependence and the thickness of the boundary. A more involved but consistent treatment provides the same results within the accepted approximation and sheds light on the reason of validity of the simplified approach.Article Citation - WoS: 2Citation - Scopus: 2Size Driven Barrier To Chirality Reversal in Electric Control of Magnetic Vortices in Ferromagnetic Nanodiscs(Royal Society of Chemistry, 2022) Aldulaimi, W. A. S.; Okatan, Mahmut Barış; Şendur, Kürşat; Onbaşlı, Mehmet Cengiz; Mısırlıoğlu, İbrahim BurçNew high density storage media and spintronic devices come about with a progressing demand for the miniaturization of ferromagnetic structures. Vortex ordering of magnetic dipoles in such structures has been repeatedly observed as a stable state, offering the possibility of chirality in these states as a means to store information at high density. Electric pulses and magnetoelectric coupling are attractive options to control the chirality of such states in a deterministic manner. Here, we demonstrate the chirality reversal of vortex states in ferromagnetic nanodiscs via pulsed electric fields using a micromagnetic approach and focus on the analysis of the energetics of the reversal process. A strong thickness dependence of the chirality reversal in the nanodiscs is found that emanates from the anisotropy of the demagnetizing fields. Our results indicate that chiral switching of the magnetic moments in thin discs can give rise to a transient vortex-antivortex lattice not observed in thicker discs. This difference in the chirality reversal mechanism emanates from profoundly different energy barriers to overcome in thin and thicker discs. We also report the polarity-chirality correlation of a vortex that appears to depend on the aspect ratio of the nanodiscs.Article Citation - WoS: 4Citation - Scopus: 4Chirality Switching in Ferromagnetic Nanostructures Via Nanosecond Electric Pulses(Wiley-VCH Verlag, 2021) Aldulaimi, W. A. S.; Akaoğlu, C.; Şendur, Kürşat; Okatan, Mahmut Barış; Mısırlıoğlu, İbrahim BurçThe stability of magnetism in reduced dimensions has become a major scientific agenda in the pursuit of implementing magnetic nanostructures as functional components in spintronic devices. Methods to probe and control magnetization states of such structures in a deterministic manner include use of spin polarized currents, photon absorption, and relatively recently, electric fields that tailor magnetoelectric coupling in multiferroic based structures. In theory, a short electric pulse is able to generate localized magnetic fields that can couple to the local magnetic dipoles electrodynamically. Here, using the Landau-Lifshitz-Gilbert formalism of magnetism dynamics combined with continuum Maxwell relations, the response of a ferromagnetic permalloy nanodisc to nanosecond electric field pulses is studied. The dynamics of the magnetic order of the nanodiscs during this process are examined and discussed. Ferromagnet nanodiscs, when below a critical size and in the absence of any external field, relax to a vortex phase as the ground state due to the demagnetizing field. Simulations demonstrate that the planar chirality of such a ferromagnet nanodisc can be switched via a time-wise asymmetric electric field pulse on the order of a few ns duration that generates radially varying tangential magnetic fields. These fields couple to the vortex state of the nanodisc ferromagnet electrodynamically, revealing an effective and robust method to control chirality.