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    Electric Field-Induced Strain Behavior in Lithium- and Copper-Added Potassium Sodium Niobate Piezoceramics and 1-3 Piezocomposites
    (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2011) Alkoy, Ebru Mensur; Berksoy, Ayse; Tekdas, A. Serkan
    Potassium sodium niobate (KNN)-based lead-free materials were prepared and their field-induced strain behaviors were investigated. Ceramic lead-free piezoelectric materials were prepared in bulk and fiber forms with 1 mol% CuO-added potassium sodium niobate K(0.5)Na(0.5)NbO(3) and x = 7 mol% lithium-modified (K(0.5-x/2) Na(0.5-x/2)Li(x))NbO(3) compositions. Fibers were drawn using a novel alginate gelation technique. Piezocomposites were prepared from these fibers with 1-3 connectivity and an epoxy matrix. A fully recoverable electrostrain of up to approximately 0.11% was observed in the CuO-added sample, whereas the Li-modified sample yielded up to 0.10% at 50 kV/cm electric field. A strain value of up to approximately 0.03% at 50 kV/cm electric field was obtained for piezocomposites prepared from lithium-modified fibers. The high-field converse piezoelectric coefficient was calculated from the strain-electric field (x-E) graph for all samples. Strain characteristics of the bulk and piezocomposite samples were analyzed based on the variation of strain with respect to square of the polarization (x-P(2)) to determine the electrostrictive contribution to the strain.
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    Electrical Properties of 1-3 Piezocomposites with Potassium Sodium Niobate Fibers
    (TAYLOR & FRANCIS LTD, 2011) Alkoy, Ebru Mensur; Tekdas, A. Serkan; Berksoy, Ayse
    Lead-free 1 mole% CuO-added potassium sodium niobate K0.5Na0.5NbO3 (KNN) fibers were drawn using a novel alginate gelation technique. Piezocomposites with 1-3 connectivity were prepared with an epoxy matrix with various fiber volume fractions (V-f). The dielectric constant of the piezocomposites were found to increase from 67 to 190 with the addition of CuO into KNN and increasing Vf in the 1-3 piezocomposite. A fully recoverable electrostrain of 0.023% for the piezocomposites with V-f = 0.63 under an electric field of 4 kV/mm. A very high electrostrictive Q(33) coefficient of 162x10(-3) m(4)/C-2 was obtained from piezocomposites.
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    Preperation of Lead-Free Potassium Sodium Niobate Based Piezoelectrics and Their Electromechanical Characteristics
    (TRANS TECH PUBLICATIONS LTD, 2012) Berksoy, Ayse; Mensur Alkoy, Ebru; Yigit, F; Hashmi, MSJ
    In this study, %7 Li modified and 0.67% copper oxide added potassium sodium niobate (KNN) ceramics were investigated. Copper oxide was used as a sintering aid. The ceramics were prepared with conventional solid state calcination technique. All samples were crystallized in pure perovskite phase with no additional peak. The density of the samples increased with copper addition and lithium modification. The Curie temperature of KNN ceramics was found to shift to lower temperatures by CuO addition. The Curie temperature was measured as 414 degrees C and 504 degrees C for copper oxide added and lithium modified KNN samples, respectively. The maximum strain of copper oxide added sample was 0.12%, whereas Li modified KL ceramics yielded up to 0.10%.