Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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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: 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: 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: 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.