Master Degree / Yüksek Lisans Tezleri

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Access Right: Open AccessAuthor: search.filters.author.Demirtay, Tuğçe

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  • Master Thesis
    Determination of the Electrocalorinc Properties of the Ferroelectric (1-x)batio3-bi(li1/3ti2 (0?x?0.2) System
    (Izmir Institute of Technology, 2018) Demirtay, Tuğçe; Adem, Umut; Çiftçioğlu, Muhsin
    The aim of this study is to develop electrocaloric (EC) materials for alternative eco-friendly cooling technologies. Considering the dielectric and piezoelectric properties of the (1-x)BaTiO3- xBi(Li1/3Ti2/3)O3 (0≤x≤0.2), this system was selected to study electrocaloric properties due to the presence of morphotropic phase boundary (MBP). The crystal structure of the samples that were synthesized by convential solid state reaction technique were determined by the X-Ray Diffraction experiments. The electrical properties of the ceramics were characterized by temperature-dependent dielectric measurements and the phase transition temperatures of the samples were identified. Temperature-dependent electrical polarization curves were measured for all compositions and electrocaloric temperature change values were calculated with the help of Maxwell equations. Using the dielectric measurements, a phase diagram was obtained. Strain-electric field measurements were done to complement dielectric and polarization measurements. A new antiferroelectric phase was discovered at high temperatures in the samples. As Bi(Li1/3Ti2/3)O3 content is increased, phase transition from the ferroelectric to antiferroelectric phase decreases. Since in the antiferroelectric phase the net polarization is very small, a large polarization change therefore large electrocaloric temperature change is obtained. Highest electrocaloric temperature change (ΔT=0.66 K under 22 kV/cm) is obtained for x=0.03 sample.