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Actuators 2015, 4(2), 99-113;

Ferroelectric KNNT Fibers by Thermoplastic Extrusion Process: Microstructure and Electromechanical Characterization

Empa - Swiss Federal Laboratories for Materials Science and Technology, High Performance Ceramics, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland
Changwon National University, Gyeong-Nam 641-773, South Korea
These authors contributed equally to this work.
Authors to whom correspondence should be addressed.
Academic Editor: Delbert Tesar
Received: 20 March 2015 / Revised: 30 April 2015 / Accepted: 5 May 2015 / Published: 8 May 2015
(This article belongs to the Special Issue Feature Papers)
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B-site substitution in KNN with tantalum results in a higher d33 and dielectric constant. This higher value makes KNNT interesting for lead-free actuator applications. KNNT fibers with diameters of 300 and 500 μm have been extruded and sintered at 1200 °C in a KNNT-enriched atmosphere. Subsequently, the influence of fiber diameter on the microstructure (porosity and grain size) was investigated. The measurements revealed that with decreasing fiber diameter, the porosity increases, whereas the grain size decreases. The influence of these microstructural differences on the piezoelectric properties was evaluated using a novel characterization procedure for single fibers. The larger diameter fibers show an increase in the electromechanical properties measured, i.e., d33, tanδ, Pr, Ec and the free longitudinal fiber displacement, when compared to smaller diameter fibers. The lower alkali losses result in a larger grain size, a higher density during sintering and lead to higher electromechanical properties. View Full-Text
Keywords: KNNT; fibers; dielectric constant; fiber diameter KNNT; fibers; dielectric constant; fiber diameter

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Lusiola, T.; Hussain, A.; Kim, M.H.; Graule, T.; Clemens, F. Ferroelectric KNNT Fibers by Thermoplastic Extrusion Process: Microstructure and Electromechanical Characterization. Actuators 2015, 4, 99-113.

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