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In a previous work, the authors have presented a comprehensive procedure for the direct characterization of single piezoelectric ceramic fibers in terms of butterfly and polarization loops and blocking force. The ability to investigate single fibers is relevant for optimizing their manufacturing processes, for quality control purposes, and for modeling the response of components and structures. In this study the novel testing procedure is used to characterize commercially available fibers distributed by Advanced Cerametrics Inc., CeraNova Corp., and Smart Material Corp., respectively, and to compare their performance with fibers developed at Empa. Their porosity, grain size and phase composition were investigated to correlate the ferroelectric properties with the microstructure. Fibers supplied by Smart Material Corp. exhibited the best ferroelectric performance, in particular the highest saturation and remnant polarization, the lowest coercive field and the highest P-E loop squareness. The said properties result from a low porosity, a sufficiently large grain size and a phase composition near the morphotropic phase boundary. After removing a surface layer dominated by a rhombohedral phase, Empa fibers developed maximum average free-strains 15% larger than any commercially available fiber. Better control of the sintering atmosphere thus promises to be the key to very high performance fibers. [ABSTRACT FROM AUTHOR]

The characterization of the ferroelectric properties of piezoelectric ceramic fibers is paramount for optimizing their manufacturing processes, for quality control purposes, and for modeling the response of components and structures. Until now, fibers were generally characterized by measuring the so-called 1-3 composites, fiber arrays embedded in a polymer matrix. The fiber properties can then be extracted, provided the volume fraction and stiffness of each phase, the fiber piezoelectric charge constant as a function of the electrical field strength, and the matrix permittivity are known. This implies a large amount of time and experimental effort. This article presents a comprehensive procedure for the direct characterization of single piezoelectric ceramic fibers in terms of butterfly and polarization loops, as well as their blocking force. The experimental setup is composed of a waveform generator, a high-voltage amplifier, a dynamic mechanical analyzer, a current/charge measuring circuit, and an oscilloscope. The active circuitry used for reliably collecting the charge generated by a single fiber is presented in full detail. The very good repeatability of the measurements showed the proposed procedure to be robust. The comparison between single fiber measurements and the investigation of 1-3 composites revealed both procedures to be equal, at 99.9%, in determining the average strain and polarization properties. In addition, the single fiber measurement provides an estimation of the variation in fiber properties within a single production batch. This information is essential to understand how to optimize processing routes and build robust devices. [ABSTRACT FROM AUTHOR]