Microwave Dielectric Properties of xMgO–(1 - x)B2O3 Ceramics.

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 xMgO–(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 xMgO–(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 xMgO–(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 xMgO–(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· f value of the ceramics was observed at x > 0.95. As a result, a maximum Q· f value of approximately 773000 GHz was obtained at x = 0.99. Such the variation in the Q· f value may be attributed to the sinterability of MgO compound, which is related to microstructural changes in the ceramics. [ABSTRACT FROM AUTHOR]