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: 3Citation - Scopus: 3Effects of Different Precursors on the Aging and Electrocaloric Properties of Mn-Doped Ba0.95sr0.05tio3 Ceramics(Springer, 2023) Karakaya, Merve; Erdem, Emre; Akdoğan, Yaşar; Adem, UmutIn this study, the effects of different types of Mn precursors (MnO2 and Mn2O3) and sintering temperature on the defect dipole formation, ferroelectric aging and electrical properties were investigated by using Ba0.95Sr0.05TiO3 ceramics as the base. Both Mn precursors were substituted to the Ti-site as 1 mol% and two different sintering temperatures of 1325 and 1400 degrees C were used to study the effect of grain size. We deduced that slightly higher amounts of Mn2+ can be incorporated into the perovskite structure when MnO2 is used as the precursor, by using X-ray diffraction and electron paramagnetic resonance spectroscopy. Mn-doped samples sintered at 1325 degrees C age faster than those sintered at 1400 degrees C. Aging caused a decrease in the electrocaloric effect whereas Mn-doping increased it. This study shows that Mn precursor used for the acceptor doping affects the amount of Mn incorporated into the structure and therefore electrical properties of the resulting ceramics.Article Citation - WoS: 9Citation - Scopus: 9Cold Sintering Assisted Two-Step Sintering of Potassium Sodium Niobate (knn) Ceramics(Elsevier, 2023) Karacasulu, Levent; Ahmetoğlu, Çekdar VakıfPotassium sodium niobate (KNN) ceramics were densified using a multiple-stage sintering process in which initially applied cold sintering process (CSP) was followed by the solid-state sintering between 1100 and 1120 °C. Comparative assessments demonstrated that multi-step sintered samples yielded better properties than conventionally sintering ones. The highest relative density (94.7%) and the best electrical properties were obtained from the sample subjected to cold sintering at 120 °C/1 h using 5 wt% deionized water subsequently heat-treated at 1120 °C/2 h, resulting in a monolithic KNN ceramic having a piezoelectric coefficient of 120 pC/N. © 2023 Elsevier B.V.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: 23Citation - Scopus: 27Electric Field Effects on Cnts/Vinyl Ester Suspensions and the Resulting Electrical and Thermal Composite Properties(Elsevier Ltd., 2010) Yurdakul, Hilmi; Seyhan, Abdullah Tuğrul; Turan, Servet; Tanoğlu, Metin; Bauhofer, Wolfgang; Schulte, KarlIn this study, electrical conductivity of a vinyl ester based composite containing low content (0.05, 0.1 and 0.3wt.%) of double and multi-walled carbon nanotubes with and without amine functional groups (DWCNTs, MWCNTs, DWCNT-NH2 and MWCNT-NH2) was investigated. The composite with pristine MWCNTs was found to exhibit the highest electrical conductivity. Experiments aimed to induce an aligned conductive network with application of an alternating current (AC) electric field during cure were carried out on the resin suspensions with MWCNTs. Formation of electric anisotropy within the composite was verified. Light microscopy (LM), scanning electron (SEM) and transmission electron microscopy (TEM) were conducted to visualize dispersion state and the extent of alignment of MWCNTs within the polymer cured with and without application of the electric field. To gain a better understanding of electric field induced effects, glass transition temperature (Tg) of the composites was measured via Differential Scanning Calorimetry (DSC). It was determined that at 0.05wt.% loading rate of MWCNTs, the composites, cured with application of the AC electric field, possessed a higher Tg than the composites cured without application of the AC electric field. © 2010 Elsevier Ltd.Article Citation - WoS: 24Citation - Scopus: 24Electrical and Dielectrical Properties of Tantalum Oxide Films Grown by Nd:yag Laser Assisted Oxidation(Elsevier Ltd., 2008) Aygün, Gülnur; Turan, RaşitTantalum pentoxide (Ta2O5) thin films (20 to 44 nm) have been grown by 1064 nm Nd:YAG laser oxidation of Ta deposited films with various thickness on Si. Fourier Transform Infrared (FTIR) spectrum, thickness distribution, dielectric and electrical properties of laser grown oxide layers have been studied. The effect of the sputtered Ta film thickness, laser beam energy density and the substrate temperature on the final Ta2O5 film structure has been determined. It is shown that the oxide layers obtained for the laser beam energy density in the range from 3.26 to 3.31 J/cm2 and the substrate temperature around 350 °C have superior properties. FTIR measurement demonstrates that the Ta2O5 layers are obtained with the laser assisted oxidation technique. Metal Oxide Semiconductor capacitors fabricated on the grown oxide layers exhibits typical Capacitance-Voltage, Conductance-Voltage and Current-Voltage characteristics. However, the density of oxide charges is found to be slightly higher than the typical values of thermally grown oxides. The conduction mechanism studied by Current-Voltage measurements of the capacitors indicated that the current flow through the oxide layer is modified Poole-Frenkel type. It is concluded that the Ta2O5 films formed by the technique of Nd:YAG laser-enhanced oxidation at relatively low substrate temperatures are potentially useful for device applications and their properties can be further improved by post oxidation annealing processes. © 2008 Elsevier B.V