| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 1618835 | Journal of Alloys and Compounds | 2011 | 5 Pages |
Low loss dielectrics based on two borate glasses, (13–19)CaO·(13–19)La2O3·68B2O3 and (13–19)ZnO·(13–19)La2O3·68B2O3, have been investigated with a focus on effects of the CaO/La2O3 and ZnO/La2O3 ratios on physical and dielectric properties. All samples were prepared by mixing glass with 40 wt% Al2O3 filler and by firing at 850 °C for 30 min. The effects of increasing relative contents of Ca and Zn were found to be opposite specifically in microstructure evolution and crystallization behavior, and thus, dielectric properties. For example, the 13CaO·19La2O3·B2O3 sample having the lowest Ca content showed the highest Q × f of ∼8100, while the 19ZnO·13La2O3·B2O3 sample having the highest Zn content showed the highest Q × f of ∼18,100. The extensive crystallization of low loss phases, i.e., LaBO3 and LaAl2.03(B4O10)O0.54, as well as the improved level of densification are assumed to be responsible for better dielectric performance.
Research highlights▶ Low loss dielectrics based on two borate glass systems, (13–19)CaO·(13–19)La2O3·68B2O3 and (13–19)ZnO·(13–19)La2O3·68B2O3, are investigated by focusing on effects of the CaO/La2O3 and ZnO/La2O3 ratios on the physical and dielectric properties. Identical compositions have not been reported so far. ▶ The effects of increasing the relative content of Ca and Zn were found to be opposite specifically in microstructure evolution and crystallization behavior, and, thus, dielectric properties. It suggests that the glass modifiers can be very critical in controlling the densification and crystallization behavior. ▶ In the CaO·La2O3·B2O3 samples, the lower content of Ca is preferred since densification is enhanced and more LaBO3 phase is produced. ▶ In the ZnO·La2O3·B2O3 samples, on the contrary, the higher content of Zn seems to be more effective in generating a larger difference between the softening and crystallization temperatures, and, hence, better densification with least porosity. ▶ As the best glass composition, 19ZnO·13La2O3·68B2O3 having the increased content of the LaAl2.03(B4O10)O0.54 phase exhibited promising dielectric properties of k ∼ 7.4 and Q × f ∼ 18,100.
