| Autor: |
Dias, Anderson, Bijumon, Pazhoor Varghese, Sebastian, Mailadil Thomas, Moreira, Roberto Luiz |
| Předmět: |
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| Zdroj: |
Journal of Applied Physics; 10/15/2005, Vol. 98 Issue 8, p084105, 8p, 1 Black and White Photograph, 2 Charts, 6 Graphs |
| Abstrakt: |
Complex ceramics Ca5-xBaxNb2TiO12 and Ca5-xBaxTa2TiO12 were prepared by conventional solid-state ceramic route. The crystalline structures were determined by x-ray diffraction, which showed that solid solutions were formed for x=4 (CaBa4Nb2TiO12 and CaBa4Ta2TiO12) and crystalline multiphases appeared for 1<=x<=3. The dielectric properties of the sintered ceramics were measured in the microwave frequency range. The dielectric constant and temperature variation of resonant frequency increased and the quality factor decreased with increasing x value. Raman analyses showed different spectra depending upon the composition, with variations in both intensity and frequency, as well as in the number of bands strictly related to the phases present. For both Nb- and Ta-based systems, the results indicated an increase in the short-range ordering with barium substitution, which explained the reduction in the unloaded quality factor (Qu). The results of far-infrared spectroscopy agree well with the Raman data, with few variations when Nb replaces Ta, and an increase in the complexity of the vibrational modes for Ca/Ba mixed ceramics. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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