A study of electro-active properties of polymer/ceramic comosites

Abdullah, Mat Johar (1990) A study of electro-active properties of polymer/ceramic comosites. PhD thesis, Prifysgol Bangor University.

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Ceramic-polymer composites with different compositions have been prepared and their electrical properties (absorption current, quasi-steady-state conduction current, dielectric and pyroelectric behaviour) have been studied. In addition, similar measurements have been made on a commercially available ceramic-polymer composite, PIEZEfM. The ceramics used include Lead Zirconate Titanate (PZT) and Barium Titanate (BaTi03) while the polymers were Polyvinylidene Fluoride (pVDF), copolymer of Vinylidene Fluoride-Trifluoroethylene (VDF-TrFE) and Polypropylene (PP). Analysis of data revealed that the process of charging and discharging currents of the composites involves charge carrier hopping through localised states (trapping sites) distributed throughout the bulk whereas the steady-state electrical conduction in these composites may originate from an ionic hopping mechanism. Dielectric properties of the composites in the frequency range of 10Hz to 100KHz have been measured using an a.c. bridge technique. Results show that the dielectric loss process is dominated by the polymer phase whereas the ceramic phase may have a significant contribution at low frequencies and high temperatures. With the increase of ceramic content in the composite, dielectric permittivity and loss were observed to increase. Measured dielectric permittivities of the composites were generally in agreement with the calculated values. The pyroelectric activity of the composites has been measured by the direct method. For samples with a high content of ceramic phase, calculated pyroelectric coefficient data appear to be comparable to those observed. The inherent high pyroelectric activity of the composites is essentially due to the ceramic phase while the high dielectric permittivity of the polymer is required to maintain a large dielectric displacement flux in the medium. Higher pyroelectric activity has been achieved in PZfSNDF-TrFE (or PZTS/PVDF) composites in comparison with that of the other composites in the present work. The pyroelectric figure of merit in these particular composites was found to be about four times higher than that of the single phase ceramic.

Item Type: Thesis (PhD)
Subjects: Degree Thesis
Departments: College of Physical and Applied Sciences > School of Electronic Engineering
Degree Thesis
Date Deposited: 25 Aug 2015 10:00
Last Modified: 16 Mar 2016 13:53
URI: http://e.bangor.ac.uk/id/eprint/5280
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