Low firing temperature zinc molybdate ceramics for dielectric and insulation applications

Low temperature firing, non-stoichiometric zinc molybdate (11ZnO-10MoO3) dielectric ceramics (NSZM) were prepared by the mixed oxide route with additions of B2O3. All products were sintered at 850-950 °C to over 96% theoretical density with co-existence of ZnMoO4 and Zn3Mo2O9 phases. The addition of B2O3 reduced the proportion of Zn3Mo2O9 secondary phase. The relative permittivities of NSZM samples ranged from 9.2 to 11.1; the breakdown strength was between 14.3 and 17.6 kV/mm. Impedance spectroscopy suggested that charge transport in the grain boundary region governed the breakdown strength. NSZM prepared with 1.0 wt% B2O3 exhibited a relative permittivity of 11.1, dielectric strength of 17.6 kV/mm, thermal expansion coefficient of 4.7 ppm/K and thermal conductivity of 1.3 W/(m K). The results indicate that NSZM is a promising candidate for dielectric and high temperature insulation applications.