Grain Size Effect on Crystal Structure and Dielectric Properties of 0.94(Bi0.5Na0.5)TiO3-0.06BaTiO3 Piezoelectrics
| Autor: | Yu-Ju Kao, 高育儒 |
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| Rok vydání: | 2008 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 96 Because the tendency of electronic industry is towards miniaturization, all the components in products have to decrease their size and enhance their performance. For electroceramics, the miniaturization of electroceramic components is accompanied by the necessity of reducing of the grain size, and it leads to begin investigating the grain size effect on properties. (Bi0.5Na0.5)TiO3 is a popular and excellent material system in lead-free piezoelectric materials because of its advantage in free control atmosphere and no lead pollution during heat treatment. In this study, 0.94(Bi0.5Na0.5)TiO3-0.06BaTiO3 is a composition within morphotropic phase boundary (MPB). It was prepared by solid state reaction method. The dense ceramics with various grain size distributions were prepared by adjusting process. And grain size effect on crystal structure, dielectric, ferroelectric and piezoelectric properties were studied in detail. The results show that: First, the range of average grain size is from 0.28 mm to 1.20 mm, and the relative density of ceramics can achieve 95% at least. Second, the domain width decreases with decreasing grain size through TEM observation, and it is found that domain walls couple to grain boundary will make the alignment of dipoles and domain walls difficult in small-grain-size ceramics. Third, the variation in grain size doesn’t adjust the crystal structure significantly in this study. Fourth, dielectric constant (er) is dominated by space charge and the volumetric percent of grain boundary. Fifth, the temperature of phase transformation (Td and Tm) decreases with decreasing grain size. Sixth, dielectric constant (eT33/ eo), remnant polarization (Pr), piezoelectric coefficient (d33), and electromechanical coupling factor (kp) are dominated by the density of domain wall and the degree of alignment of dipoles. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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