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    Electrical properties, EPR analyses and defect chemistry of Mn-doped 0.675PMN-0.325PT piezoceramics
    (Elsevier Science Ltd, 2020) Berksoy Yavuz, Ayşe; Mensur Alkoy, Ebru; Erdem, Emre; Alkoy, Sedat
    The morphotropic phase boundary solid solution of 0.675Pb(Mg1/3Nb2/3)O-3 -0.325PbTiO(3) (0.675PMN-0.325PT) were studied. Manganese (Mn) was used as a dopant element in 0.4 mol% and 0.7 mol% ratios because of its multiple oxidation states. Sintering was done either in the air or under an oxygen-rich atmosphere. Both the effect of doping and sintering atmosphere on the electrical properties were reported. The ceramic with 0.4 mol% were exhibited higher properties such as piezoelectric charge coefficient (d(33)), dielectric constant, polarization values compared to undoped and 0.7 mol% Mn-doped ceramics. Electron paramagnetic resonance (EPR) spectroscopy was used to resolve the oxidation state of Mn in the 0.675PMN-0.325PT structure. The electrical properties were discussed and explained using defect chemistry.
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    Structural and electrical properties of ⟨001⟩ textured 0.26PIN-0.40PMN-0.34PT ternary system
    (Springer, 2019) Berksoy Yavuz, Ayşe; Mensur Alkoy, Ebru; Gözütok, Ebru; Dursun, Sinan; Yılmaz, Hüseyin; Alkoy, Sedat
    Lead indium niobate (PIN)-lead magnesium niobate (PMN)-lead titanate (PT) solid solution in the ratio of 0.26PIN-0.40PMN-0.34PT was fabricated by tape-casting in random and < 001 > (pc) textured forms. PIN-PMN-PT was textured using 5 vol% barium titanate templates. The Lotgering factor, f, of 0.26PIN-0.40PMN-0.34PT textured ceramics was approximately calculated as 95%. Quenching from above the Curie temperature down to the room temperature was applied to both random and textured samples, which led to drastic increases in the ferroelectric and piezoelectric properties. The Curie temperature, dielectric constant (epsilon(r)), converse piezoelectric charge coefficient (d33*) and piezoelectric voltage constant (g(33)) of textured and quenched sample were found to be 223 degrees C, 2455, 1432 pm/V and 27.60 x 10(-3) Vm/N, respectively.
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    Structural features and energy harvester device applications of textured 0.675 PMN-0.325 PT piezoceramics
    (Springer, 2020) Berksoy Yavuz, Ayşe; Savacı, Umut; Turan, Servet; Alkoy, Sedat; Mensur Alkoy, Ebru
    In the current study, textured lead magnesium niobate-lead titanate solid solution with composition 0.675Pb(Mg1/3Nb2/3)O-3-0.325PbTiO(3) (0.675PMN-0.325PT) has been fabricated with 0.7 mol% manganese (Mn) doping to enhance the soft character and the figure of merit (FOM). Random and textured PMN-PT plates were prepared by tape casting where 1 vol% plate-like barium titanate (BaTiO3) single-crystal templates were added to induce texture. A detailed structural investigation using scanning/transmission electron microscopy (STEM) and precession electron diffraction techniques has been conducted to establish the orientational relationship between the PMN-PT matrix and the BT templates. The FOM of textured and doped PMN-PT was found to increase for almost fourfold compared to random undoped case. Characterization of the energy harvesting (EH) performance of unimorph EH devices indicated an over twofold increase in the output power of the doped and textured case in comparison to the undoped and random PMN-PT ceramics.
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    Temperature dependent electrical and electrocaloric properties of textured 0.72PMN-0.28PT ceramics*
    (Taylor & Francis Ltd, 2022) Böbrek, İrem; Berksoy Yavuz, Ayşe; Kaya, Mustafa Yunus; Alkoy, Sedat; Okatan, Mahmut Barış; Mısırlıoğlu, İbrahim Burç; Mensur Alkoy, Ebru
    Lead 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.