Microwave composite dielectrics based on magnesium titanates

Composite dielectrics comprising the crystal phases of Co-doped magnesium titanates MgTiO3 and Mg2TiO4, and CaTiO3 were examined with regard to their phase composition and its effect on the microwave dielectric properties. In the case of MgTiO3-based composites an increase in the Co concentration results in increasing amount of an additional phase MgTi2O5, which significantly deteriorates the product Q × f. In contrast, the materials based on the spinel Mg2TiO4 never contain MgTi2O5, and consequently demonstrate excellent Q × f magnitude which is as high as 100,000 GHz at low Co doping. At higher Co concentration, however, an additional phase MgTiO3 appears in these materials that is accompanied by a slight reduction of the Q × f magnitude. A slight addition (5 wt.%) of the glass-forming zinc borate into the Mg2TiO4-based composite allows a noticeable reduction of its sintering temperature by 150–200 °C without a significant degradation of its dielectric properties.