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    Characterization of 1-3 piezocomposites from PNN-PZT piezoceramics
    (Elsevier Science Sa, 2023) Yalcin, Ezgi; Gozuacik, Namik Kemal; Alkoy, Sedat; Sari, Huseyin Alptekin; Kaya, Mustafa Yunus; Oncel, Cinar; Mensur, Ebru
    Piezocomposite materials combine best properties of components while minimizing their disadvantages to provide desired properties. This study reports on piezocomposites with 1-3 connectivity prepared from 0.5Pb (Ni1/3Nb2/3)O3-0.5Pb(Zr0.3Ti0.7)O3 (0.5PNN-0.5PZT) fibers and polyurethane matrix. The PNN-PZT powder was synthesized by solid-state reaction method. PNN-PZT green fibers were drawn using the alginate gelation method. Dense sintered fibers with 500-800 mu m diameter were embedded in an ordered arrangement in a polyurethane passive matrix. Structural, electrical and electroacoustic properties of PNN-PZT piezocomposite and bulk ceramic were both reported. Bulk PNN-PZT ceramics were found to have properties that are superior than the commercial soft PZT counterparts. The maximum TVR value was measured as 142.5 dB at 444 kHz for the piezocomposite, corresponding to the thickness mode resonance. The FFVS response with 3 dB variation had an average FFVS value of - 210 dB between 250 and 450 kHz band for the piezocomposite.
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    Design, finite element analysis, fabrication and electroacoustic characterization of transducer arrays from piezoceramics with hollow cylindrical shell form
    (Taylor & Francis Ltd, 2022) Boz, Muhammet; Kaya, Mustafa Yunus; Ozdemir, Omer; Alkoy, Sedat
    Electroacoustic transducers arrays operating in the 50-100 kHz frequency range are currently being investigated for underwater applications such as target detection transducers installed on underwater autonomous vehicles (UAV) and detection of underwater intruders to protect and secure economically and strategically critical coastal areas and facilities. However, the frequency range is such that it prevents the use of monolithic piezoceramics operating in the thickness mode due to the unacceptably high voltages that are required to drive them. Whereas the alternative such as Langevin-type transducer solutions have certain other assembly difficulties that arise due to the size limitations imposed on the transducer from the half-wavelength (lambda/2) arrangement requirement of the units. In our study, an entirely new alternative was proposed to overcome these difficulties. A piezoceramic transducer constructed from a hollow cylindrical shell form poled in the radial direction was designed and developed to operate at the longitudinal length extension mode. Since the hollow cylindrical piezoceramics were designed and produced with one end closed, this closed end was used as a passive cap with the transducer operating in a piston mode. ATILA finite element analysis code was used to design, analyze and fine-tune the dimensional requirements of the transducer. The center frequency of the transducer was fixed to 70 kHz. Commercial lead zirconate titanate (PZT) composition with hard piezoelectric character (PZT-4) was used as the starting powder. The slip casting method was used to obtain the cylindrical shell form. Single element transducers, as well as a hexagonal close-packed array consisting of seven units and arranged with a distance of half-wavelength (lambda/2) to obtain constructive interference at 70 kHz were constructed and tested for underwater electroacoustic performance.
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    Design, Modeling and Fabrication of a Novel Class V Flextensional Transducer: The Sea-Shell
    (Ieee-Inst Electrical Electronics Engineers Inc, 2023) Kaya, Mustafa Yunus; Alkoy, Sedat
    In this study, a novel class V flextensional transducer (FT) was developed by assembling symmetrically convex ceramic and metal caps to form a seashell-like structure. The transducer was designed and analyzed using ATILA finite element analysis (FEA) software. The diameter, thickness, and radius of curvature of the ceramic and metal shells have been investigated as design parameters. The transducer was found to display four distinct flextensional modes in addition to the main radial resonance mode between 1 and 200 kHz frequency range. Prototypical devices were fabricated from four different commercial lead zirconate titanate (PZT) compositions and underwater performances were compared. Transmitting voltage responses (TVRs) were observed to range between 120 and 135 dB (ref 1 mu Pa/V) at frequencies above 50 kHz.
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    Lead-based antiferroelectrics revisited for high energy density capacitors and large strain actuators
    (Taylor and Francis Ltd., 2021) Sarı, Hüseyin Alptekin; Gözüaçık, Namık Kemal; Kaya, Mustafa Yunus; Menşur, Ebru; Alkoy, Sedat
    Lead zirconate stannate titanate (PZST) ceramics with the generic composition of Pb1-0.5xNbx[(ZrySn1-y)1-zTiz]1-xO3 with x representing Nb content (x = 0 or 0.02), y representing Zr:Sn ratio (y = 0.57 or 0.60), and z representing Ti content (z = 0.06 or 0.08), and lead lanthanum zirconate titanate (PLZT) ceramics with the general composition of Pb1-xLax(ZryTi1−y)1−x/4O3 with x = 0.050 − 0.120 were synthesized using solid state reaction method and sintering. The energy density and field induced strain behavior of these compositions were investigated for capacitor and actuator applications, respectively. The focus of the study was to evaluate and discuss the change in the polar state of these ceramics from normal ferroelectric to antiferroelectric to relaxor antiferroelectric to linear dielectric with compositional modification. The highest releasable energy density (1.053 J/cm3) was obtained from the antiferroelectric Pb[(Zr0.60Sn0.40)0.94Ti0.06]O3 composition among the PZST compositions that were investigated, but the efficiencies were generally low (max. 60%) due to the large hysteresis that was observed in these compositions. The highest field induced strain level of 0.26% was also measured in the same composition. In the case of PLZT compositions, the highest releasable energy density values (0.313 J/cm3) with much higher efficiencies (76%) and highest field induced strain levels (0.23%) were obtained from the PLZT compositions with relaxor antiferroelectric character.
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    Temperature Dependent Electrical and Electrocaloric Properties of Textured 0.72PMN - 0.28PT Ceramics*
    (Taylor and Francis Ltd., 2021) Bobrek, Irem; Berksoy-Yavuz, Ayse; Kaya, M. Yunus; Alkoy, Sedat; Okatan, M. Baris
    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 (d33*) 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 (ΔTEC) of ∼0.5 K was calculated from the PMN-28PT ceramics at around 80 °C under an electric field of 60 kV/cm. Development of texture was demonstrated to have led to an anisotropy in the EC response.