Microwave dielectric properties of Mg4Nb2O9 ceramics produced by hydrothermal synthesis

Mg 4 Nb 2 O 9 ceramics have been prepared by a hydrothermal synthesis in order to reduce the sintering temperature. The sintering and microwave dielectric properties of the hydrothermally processed Mg 4 Nb 2 O 9 were studied under various sintering temperatures ranging from 900 to 1300°C. The highest Q × f o value of 26,069 GHz was obtained at the sintering temperature of 1300°C and is attributed to the increased density and appropriate grain growth. τ f value of −17.1 ppm/°C was improved by the addition of TiO 2 and τ f value of 6.7 ppm/°C was obtained at 20 wt% TiO 2 . Chemical compatibility of Mg 4 Nb 2 O 9 with Ag was tested to identity the possibility of using Mg 4 Nb 2 O 9 for an LTCC application. Since any secondary phase was not observed in the XRD pattern of the mixtures of Mg 4 Nb 2 O 9 and Ag powder heat treated at 900°C, it was considered that the Mg 4 Nb 2 O 9 system is applicable to the multilayer microwave devices using Ag as an electrode.