1,720,997 research outputs found
Influence of aging on electrocaloric effect in Li+ doped BaTiO3 ceramics
Get PDFAging creates significant changes in the properties of the ferroelectric materials such as dielectric and
piezoelectric properties. However, the influence of aging on the electrocaloric effect (ECE) has not yet
been investigated. In this work, we investigate the effect of the aging on the ECE in acceptor (Liþ) doped
BaTiO3 ceramics. We observe that aging induced defect polarization (PD) reduces the saturation polarization of the doped samples until Tc ¼ 115 C. Above that temperature PD loses its effectiveness and
material behaves like a fresh sample. Suppression of polarization below TC due to aging effect results in a
sharper slope change in the temperature dependence of electrical polarization in aged samples which
causes an increase in the electrocaloric temperature change of Liþ doped BaTiO3 ceramics up to 23% at TC.
Above a critical Li doping amount, both negative and positive electrocaloric effect are observed in the
same sample
Electrocaloric properties of Ba0. 8Sr0. 2Ti1-xZrxO3 (0≤ x≤ 0.1) system: The balance between the nature of the phase transition and phase coexistence
Get PDFWe investigate the electrocaloric effect of Ba0.8Sr0.2Ti1-xZrxO3 (0 ≤ x ≤ 0.1) system by comparing the electrocaloric temperature change (ΔT) of different compositions belonging to the different regions of the phase diagram. We show that as the amount of Zr increases, electrocaloric temperature change initially decreases as the phase transition gets diffuse then increases again as the composition of the samples are located closer to the critical point where different ferroelectric phases coexist. Since the critical point is reached at relatively low Zr substitution levels (i.e. around x = 0.07), the phase transition doesn't get too diffuse and thefore the compositions between x = 0 and x = 0.10 (which contains higher Zr than the critical point composition) have comparable ΔT values. Electrocaloric efficiency of these compositions (x = 0.03, 0.05 and 0.07) is around 0.20 K mm/kV at 20 kV/cm. We discuss the results in terms of the balance between the nature of the phase transition and proximity to the critical point, based on the phase diagram.TUBITAK (315M241
Influence of aging on electrocaloric effect in Li+ doped BaTiO3 ceramics
No full textAging creates significant changes in the properties of the ferroelectric materials such as dielectric and piezoelectric properties. However, the influence of aging on the electrocaloric effect (ECE) has not yet been investigated. In this work, we investigate the effect of the aging on the ECE in acceptor (Li+) doped BaTiO3 ceramics. We observe that aging induced defect polarization (P-D) reduces the saturation polarization of the doped samples until T-c=115 degrees C. Above that temperature P-D loses its effectiveness and material behaves like a fresh sample. Suppression of polarization below T-C due to aging effect results in a sharper slope change in the temperature dependence of electrical polarization in aged samples which causes an increase in the electrocaloric temperature change of Li+ doped BaTiO3 ceramics up to 23% at T-C. Above a critical Li doping amount, both negative and positive electrocaloric effect are observed in the same sample. (C) 2019 Elsevier B.V. All rights reserved
Multiferroic Materials: Physics and Properties
No full textMultiferroics are materials in which magnetism and ferroelectricity coexist. They are of fundamental interest to understand electronic behavior coupling magnetic interactions and electric dipolar order. Moreover, they are of applied interest because they allow various types of novel magnetic and electric device structures. We distinguish two important classes of multiferroic materials and discuss mechanisms and materials belonging to each class separately. In the first group of multiferroics, magnetization and polarization arise independently from each other. In the second category of multiferroics, ferroelectricity is induced by magnetic order, resulting in strong magnetoelectric coupling. We also briefly discuss multiferroic thin film heterostructures showing interfacial magnetoelectric coupling interactions with potential applications in memory devices
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Magnetodielectric coupling in multiferroic transition metal oxides
Get PDFThe study of materials that show cross-coupling effects between magnetization and electrical polarization (thus dielectric constant), has become one of the most popular areas in the field of solid state physics since the discovery of large magnetoelectric coupling in TbMnO3 in 2003. The revival of research into materials that show this cross-coupling effect, namely, magnetoelectrics and multiferroics, coincided with the integration of ferroelectric thin films and new high-k dielectrics in Si technology starting in the 1990s. These materials in thin film form could allow the coupling of polarization P to magnetization M, which can be potentially exploited for multiple-state memory elements. However, utilizing multiferroics as new multistate memory elements is not yet possible since the magnetic (electric) fields necessary to switch the electric (magnetic) state of the materials are too high to be used in memory devices due to the weak cross-coupling effects. This thesis aims to understand magneto(di)electric coupling in transition metal oxides. We have measured the magnetodielectric response of different known as well as novel materials and studied the effects of the magnetic symmetry and the structural changes on the magneto(di)electric coupling. Our studies provide valuable insight into the fundamental mechanisms of the coupling, which is necessary to understand the interplay of phonons, magnetism and electrical dipoles.
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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