Synthesis And Study On Properties Of MgTiO₃-Based Microwave Dielectric Ceramics With High Q Value

The MgTiO₃ microwave dielectric ceramic with low dielectric loss, abundant raw materials source and low cost, the resonant frequency of which is about 10 GHz, has attracted much attention. Through the ways such as two phase composite, ion doping, adding sintering additives, the sintering characteristic and microwave dielectric properties of MgTiO₃-based ceramic prepared via the conventional solid-state reaction route have been investigated. The main study included as follows:Firstly, the microstructures and microwave dielectric properties of Zn-excess MgTiO₃ ceramics, Mg_0.97Zn_0.03+xTiO_3+x?x=0.000-0.030?, were investigated. The results show that Zn-excess restrains the formation of second phase MgTi₂O₅ and that Zn-excess promote the ceramic sintering, lower the sintering temperature and improve the microwave dielectric properties. When x=0.005, Mg_0.97Zn_0.03+xTiO_3+x?x=0.005? ceramic sintered at 1250?/4h has the best excellent dielectric properties: ?r = 17.66, Q×f = 277,500 GHz, ?f =-55.09×10-6/?. CaTiO₃ addition can adjust the ?f value of Mg_0.97Zn_0.03+xTiO_3+x?x=0.005?. When the amount of CaTiO₃ addition is up to 7.0wt%, the ?f value can achieve near zero with excellent dielectric properties: ?r = 20.98,Q×f = 80,900 GHz,?f = +0.77×10-6/?.Secondly, effects of LaAlO₃ additive?1.0 mol%? on 0.95 MgTiO₃-0.05 CaTiO₃?95MCT? ceramics were investigated. The Q×fvalue of 95MCT-1.0mol% LaAlO₃ ceramics is 30% higher than 95 MCT ceramics. 95MCT-1.0mol% LaAlO₃ ceramics can be sintering densification at 1225?,with good dielectric properties: ?r = 21.68, Q×f = 73,300 GHz, ?f =-2.22×10-6/?.Finally, effects of B₂O₃ aid on sintering behavior and dielectric properties ceramics of 95MCT-1.0mol% LaAlO₃ were investigated. And the microstructures were studied. The results show that all the ceramics have MgTiO₃ and CaTiO₃, and when the amount of B₂O₃ addition is up to2.0wt%, CaLa₄Ti₄O₁₅ was formed. B₂O₃ aid can effetely lower the sintering temperature of 95MCT-1.0mol% La Al O3 ceramics. When the amount of B₂O₃ addition is 1.5wt% and 3.0wt%, the ceramics can be sintered densification at 1150? with excellent dielectric properties. 1.5wt% B₂O₃ addition: ?r = 21.08, Q×f = 53,530 GHz, ?f =-1.55×10-6/?, 3.0wt% B₂O₃ addition: ?r = 20.51, Q×f = 54,700 GHz, ?f =-2.99×10-6/?.