Full metadata record
| DC Field | Value | Language |
|---|---|---|
| dc.contributor | Department of Applied Physics | en_US |
| dc.creator | Zhang, Qingqi | - |
| dc.identifier.uri | https://theses.lib.polyu.edu.hk/handle/200/283 | - |
| dc.language | English | en_US |
| dc.publisher | Hong Kong Polytechnic University | - |
| dc.rights | All rights reserved | en_US |
| dc.title | Studies on calcium and lanthanum modified lead titanate/vinylidene fluoride-trifluoroethylene [PCLT/P(VDF-TrFE)] 0-3 nanocomposites | en_US |
| dcterms.abstract | 0-3 calcium and lanthanum modified lead titanate (PCLT) / vinylidene fluoride-trifluoroethylene [(P(VDF-TrFE)] nanocomposites were fabricated. The physical structure and properties of the composites with both phases ferroelectric were studied. The investigation of the composite thin film for pyroelectric sensors application was performed. The PCLT [(Pb0.88Ca0.04La0.08)Ti0.98O3] ceramic powder that was used as ceramic phase of the composites was prepared using a sol-gel process. The structure and dispersing characteristics of the powder with crystallite size of 45 nm were investigated. An optimum solvent was found in order to prepare homogeneous PCLT/P(VDF-TrFE) composites. Ferroelectric PCLT bulk ceramics disks were prepared by sintering the PCLT powder derived from the sol-gel process and ferroelectric P(VDF-TrFE) copolymer thick films were prepared by a hot press process. The dielectric permittivities, piezoelectric and pyroelectric coefficients of these single-phase materials were measured and the data obtained were used as references in the composite modeling. The structure and phase transitions of the single-phase materials were also studied. 0-3 PCLT/P(VDF-TrFE) bulk composites with PCLT powder dispersed uniformly in a P(VDF-TrFE) matrix were fabricated using solvent-casting followed by hot-pressing. Structural analyses and electrical measurements were performed to investigate the effects and contributions of the individual phases to the composites. In the composites the XRD reflection peaks and IR vibration bands of both the ceramic and copolymer phases still appeared. The ferroelectric phase transitions of the copolymer still existed but the Curie temperature had a slight decrease. Compared to the copolymer, the 帣-relaxation peak of the composite slightly shifted to higher frequency and had broader distributions of relaxation time. Piezoelectric and pyroelectric activities of both the ceramic and copolymer phases were elicited by poling the composites at different temperatures. The piezoelectric and pyroelectric coefficients of the composites were measured and modeled. By poling the two phases in the same direction, the pyroelectric contributions from the two phases reinforced while piezoelectric contributions partially canceled, thereby minimizing the vibration induced noise. The results showed that the composites are good candidates for pyroelectric applications. To evaluate the composites for pyroelectric applications, composites in thin film form were first prepared on glass using the spin coating method and their electric properties were measured. Theoretical analyses on the performance of a multi-layered single pyroelectric detector were carried out based on the 1-D thermal diffusion equation. Silicon-based single-element and 1x8 integrated array pyroelectric sensors were fabricated with the composite as sensing materials. The current, voltage responsivites and specific detectivities of these sensors were measured and compared well with the theoretical calculations. | en_US |
| dcterms.extent | xvi, 217 leaves : ill. ; 30 cm | en_US |
| dcterms.isPartOf | PolyU Electronic Theses | en_US |
| dcterms.issued | 1999 | en_US |
| dcterms.educationalLevel | All Doctorate | en_US |
| dcterms.educationalLevel | Ph.D. | en_US |
| dcterms.LCSH | Composite materials | en_US |
| dcterms.LCSH | Fiber-reinforced ceramics | en_US |
| dcterms.LCSH | Polymeric composites | en_US |
| dcterms.LCSH | Nanostructured materials | en_US |
| dcterms.LCSH | Thin films | en_US |
| dcterms.LCSH | Hong Kong Polytechnic University -- Dissertations | en_US |
| dcterms.accessRights | open access | en_US |
Files in This Item:
| File | Description | Size | Format | |
|---|---|---|---|---|
| b14846858.pdf | For All Users | 8.02 MB | Adobe PDF | View/Open |
Copyright Undertaking
As a bona fide Library user, I declare that:
- I will abide by the rules and legal ordinances governing copyright regarding the use of the Database.
- I will use the Database for the purpose of my research or private study only and not for circulation or further reproduction or any other purpose.
- I agree to indemnify and hold the University harmless from and against any loss, damage, cost, liability or expenses arising from copyright infringement or unauthorized usage.
By downloading any item(s) listed above, you acknowledge that you have read and understood the copyright undertaking as stated above, and agree to be bound by all of its terms.
Please use this identifier to cite or link to this item:
https://theses.lib.polyu.edu.hk/handle/200/283