The Improvement And Application For Microwave Dielectric Material Of MgO-TiO₂

The MgO-TiO₂ microwave dielectric materials has attracted much attention since its low dielectric loss,abundant raw materials source and low cost.On account of the common defects of MgO-TiO₂ microwave dielectric materials,the sintering characteristic and microwave dielectric properties of the MgO-TiO₂ system have been improved through the methods such as two phase composite,ion doping,adding sintering additives.The main study and conclusion included as follows:Firstly,the original MgTiO₃-CaTiO₃ system was improved:The microstructures and microwave dielectric properties of 1.0mol% LaAlO3 doped 0.95?Mg0.95Zn0.05?TiO3–0.05CaTiO₃ ceramics were investigated.As a result,dielectric properties of the ceramic system is much higher than that of MgTiO₃-CaTiO₃ system.The optimized microwave dielectric properties with er 22.5,Q×f value 89000 GHz and a tf of ^-6.9×10-6/°C were achieved for samples sintered at 1200°C.To lower the the sintering temperature of 95MCT-1.0mol% LaAlO₃ ceramic system,B2O3 was chosen as the sintering aid.It was concluded that B₂O₃ could effectively lowered the sintering temperature of the ceramic system.With more than 2wt% B₂O₃ addition,the secondary phase CaLa4Ti₄O₁₅ was formed.The microwave dielectric properties of the ceramic system were strongly correlate with the densification as well as the phase composition.The dominant factor affecting Q×f value varied with increasing B₂O₃ addition.With 3wt% B₂O₃ addition,a maximum Q×f of 57000GHz?at 8GHz?,with a dielectric constant of 20.3 and a tf of-7.2×10-6/°C were obtained for samples sintered at 1125°C.Secondly,new microwave dielectric ceramic systems were investigated.CaTiO₃ and?Na0.5La0.5?TiO₃ could form solid solution(Ca_0.8Na_0.1La_0.1)TiO₃?CNLT?with a proper ratio.Then CNLT was used to adjust the tf value of MZT to zero.It was concluded that?1–x?MZT–xCNLT ceramic system showed a mixture of the trigonal structured MZT as a main phase,the pure orthorhombic perovskite structured CNLT as a minor phase.The microwave dielectric properties of the ceramic system were strongly correlate with the sintering temperature as well as the x value.A fine combination of microwave dielectric properties?er 22.5,Q×f ⁷9300GHz and tf 0×10-6/°C?was achieved for 93 MZTCNLT ceramics sintered at 1225°C.Moreover,CNLT was used to adjust the tf value of Mg1.8Ti1.1O4 to zero.The microwave dielectric properties of the ceramic system were strongly correlate with the sintering temperature.0.93Mg1.8Ti1.1O4-0.07 CNLT ceramic samples sintered at 1225°C showed excellent microwave dielectric properties with ?r 19.7,Q×f 68,000 GHz,?f ^-0.7×10-6/°C...