Synthesis and Microwave Dielectric Properties of MgO-xmol%B₂O₃ (x = 33 and 25) Ceramics in MgO-B₂O₃ System

Abstract

The relationships between the sintering conditions and the microwave dielectric properties of the MgO-xmol%B₂O₃ (x = 33 and 25) ceramics were investigated in this study. The XRPD profiles of MgO-33mol%B₂O₃ ceramic sintered at the temperatures higher than 1320°C exhibited the formation of two phases, i.e., MgO and Mg₃B₂O₆, which arisen from the loss of boron through volatilization; therefore, the nominal compositions of the MgO-xmol%B₂O₃ (x = 33 and 25) ceramics were changed in the sintering conditions, respectively. The dielectric constants of the the MgO-xmol%B₂O₃ (x = 33 and 25) ceramics sintered at the temperatures ranging from 1280 to 1350°C were approximately 7, whereas the Q • f values ranged from 79100 to 260100 GHz for x = 33 and from 39600 to 310000 GHz for x = 25, respectively. As a result, the highest Q • f value of the ceramic was obtained when the the MgO-33mol%B₂O₃ ceramics was sintered at 1330°C for 2 h in air. The improvement in the Q · f values of the ceramics is considered to relate with the increase in the amount of MgO phase induced by the loss of boron through volatilization. Moreover, the τ _f values of the ceramics showed the large negative values as well as the other reported microwave dielectric ceramics with high-Q.

Keywords:

• MgO
• B₂O₃
• Microwave dielectric property
• Mg₃B₂O₆
• high Q