Low-Temperature Sintering and Microwave Dielectric Properties of MgO Ceramic with LiF Addition

概要

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MgO ceramics with a nominal composition of ($1-x$)MgO--$x$LiF ($x = 0.02{\mbox{--}}0.10$) were synthesized and the effects of LiF addition and sintering conditions on the microwave dielectric properties of MgO ceramics were investigated in this study. With LiF addition, the MgO ceramics were well-sintered at 950 °C in a covered crucible, and the $Q\cdot f$ value of the LiF-added MgO ceramic strongly depended on the amount of LiF and sintering time. As a result, the MgO ceramics with a nominal composition of 0.96MgO--0.04LiF ($x=0.04$) exhibited the highest $Q\cdot f$ value of 751,500 GHz ($\varepsilon_{\text{r}} = 9.6$ and $\mathit{TCf}= - 56$ ppm/°C) when they were sintered at 950 °C for 100 h in a covered crucible. The endothermic reaction of the MgO ceramics was observed with LiF addition by differential thermal analysis and thermograviometry (DTA--TG), and it was considered that the partial melting of MgO with LiF addition to form the liquid phase enhances the sinterability of the MgO ceramics. The crystal structure analysis of the LiF-added MgO ceramics showed a slight increase in the lattice parameters of the MgO ceramics, suggesting the Li substitution for Mg in the MgO structure.
2011-09-25