Microwave Dielectric Properties of $x$MgO–($1 - x$)B2O3 Ceramics

概要

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The effects of B2O3 doping on the microwave dielectric properties of a MgO compound were characterized in this study. The MgO and Mg3B2O6 compounds were recognized in the XRPD profiles of $x$MgO–($1 - x$)B2O3 ceramics at a sintering temperature of 1350 °C for 4 h in a covered crucible. From the calculation of weight fraction of the compounds, the slight deviation in the concentrations of B2O3 and MgO from the stoichiometric composition of $x$MgO–($1 - x$)B2O3 ceramics was also observed, and was attributed to the vaporization of B2O3 and the decomposition of Mg3B2O6 compound during the sintering. In the composition range of 0.95–0.99, abnormal grain growth of $x$MgO–($1 - x$)B2O3 ceramics was observed; therefore, the decomposition of Mg3B2O6 compound into liquid phase and MgO compound may play an important role in enhancing the grain growth of the ceramics. The dielectric constant of $x$MgO–($1 - x$)B2O3 ceramics ranged from 6.9 to 9.4 depending on the amount of Mg3B2O6 and MgO compounds, whereas the remarkable variation in the $Q{\cdot} f$ value of the ceramics was observed at $x > 0.95$. As a result, a maximum $Q{\cdot} f$ value of approximately 773000 GHz was obtained at $x = 0.99$. Such the variation in the $Q{\cdot} f$ value may be attributed to the sinterability of MgO compound, which is related to microstructural changes in the ceramics.
2009-09-25