Microwave Dielectric Properties Of CaO-B₂O₃System Ceramics

With the rapid development of the mobile communications industry, it puts forwardhigher requirements on the multi-functional, high-performance and miniaturization of themobile terminal. Therefore, the development of a new type of good microwave dielectricproperties of microwave dielectric ceramic material made of ceramic components isparticularly critical. The CaO-B₂O₃system ceramics is a low dielectric constant microwavedielectric ceramics whose properties are rarely reported. This paper prepared the CaO-B₂O₃system ceramics by solid-phase sintering, and researched around their properties.Firstly, this paper studied the CaO-B₂O₃system ceramics’ sintering properties andmicrowave dielectric properties. The research results showed that the CaO-B₂O₃systemceramics’ densification temperature was1350℃. The CaO-B₂O₃system ceramics sinteredat1350℃for2h can obtain microwave dielectric properties:εr=7.4, Q×f=6968GHz,τf=-36ppm/℃.Then this paper studied the influence of doping different sintering aids on CaO-B₂O₃system ceramics’ properties with many means like XRD and SEM. The results showed thatthe addition of TiO₂, ZnO and H₃BO₃all contributed to the sintering of the CaO-B₂O₃system ceramics more or less. The main phase of CaO-B₂O₃system ceramics is Ca3B2O6.The addition of sintering aids didn’t affect its main crystalline phase.In the experimental results:（1） The microwave dielectric properties of4wt%TiO₂+CaO-B₂O₃ceramics sintering at1325℃are:εr=9.9, Q×f=10521GHz, τf=-3ppm/℃. Moreover, the addition of TiO₂can also adjust the ceramics’ temperature coefficientof frequency.4wt%TiO₂+CaO-B₂O₃ceramics sintering at1300℃can obtain τf=0ppm/℃;（2） The addition of ZnO can lower the densification temperature of CaO-B₂O₃system ceramics. The microwave dielectric properties of3wt%ZnO+CaO-B₂O₃ceramicssintering at1325℃are:εr=7.3, Q×f=5523GHz;（3） The addition of H₃BO₃can lowerthe densification temperature of CaO-B₂O₃system ceramics to1225℃. The microwave dielectric properties of2wt%H₃BO₃+CaO-B₂O₃ceramics sintering at1250℃are:εr=7.7,Q×f=10588GHz.