Giant dielectric response of the R2BaNiO5 (R = Nd, Sm, Eu, Gd, Dy, Ho, Er, and Y)
| Autor: | Keng-Wei Li, 李耿維 |
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| Rok vydání: | 2011 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 99 R2BaNiO5 (R = Nd, Sm, Eu, Gd, Dy, Ho, Er, and Y) ceramic samples were prepared by solid state reaction method at different annealing temperatures (TA), and the dielectric responses were evaluated together with the micro-structures. Powder X-ray analysis reveals the formation of a single-phase orthorhombic structure with Immm space group in all the samples. Micro-structural analysis, SEM, shows a significant change in the particle size and the morphology with TA. The dielectric constant (ε’), dielectric loss (tan δ), complex modulus (M’, M’’) and AC conductivity (σAC) were studied as a function of frequency and temperature for all the samples. The giant dielectric constant was obtained in all samples at room temperature, and strong processing and microstructure dependence of dielectric characteristics of the present ceramics was determined. All samples show a step type increase in ε’ (T) and corresponding peaks in tan δ curves. Complex modulus analysis was used to distinguish the grain and grain boundary contribution to the system, suggesting the dominance of grain boundary resistance at high temperature in all samples. The present findings would offer the great potential for enhancing dielectric constant in R2BaNiO5 ceramics by optimizing the microstructure and supplies an approach in searching for new giant dielectric constant material. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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