The microstructures and the microwave dielectric properties of the (1 - x)Mg4Nb2O9-xCaTiO(3) ceramic system were investigated. In order to achieve a temperature-stable material, CaTiO3 (tau(f) similar to 800 ppm/C) was chosen as a tau(f) compensator and added to Mg4Nb2O9(tau(f) similar to -70 ppm/degrees C) to form a two phase system. It was confirmed by the XRD and EDX analysis. By appropriately adjusting the x-value in the (1 - x)Mg4Nb2O9-xCaTiO(3) ceramic system, near-zero tau(f) value can be achieved. A new microwave dielectric material. 0.5Mg(4)Nb(2)O(9)-0.5CaTiO(3) applicable in microwave devices is suggested and possesses the dielectric properties of a dielectric constant epsilon(r) similar to 24.8. a Q x f value similar to 82,000 GHz (measured at 9.1 GHz) and a tau(f) value similar to-0.3 ppm/degrees C. (C) 2008 Elsevier Ltd. All rights reserved.