Structure and dielectric properties of Mg4Nb2O9/CaTiO3 complex dielectric ceramics

Microwave dielectric ceramics of (1-x)Mg4Nb2O9+xCaTiO3 [(1-x)MN-xCT] were prepared by conventional solid-state reaction method with 1.7% in mass V2O5 as a sintering additive. The microstructures and microwave dielectric properties of the ceramics were investigated. The results show that when 0.5x0.7, (1-x)MN-xCT samples sintered at 1150C for 5 h all have MN and CT phases without any new phases, and element diffusion exists between MN and CT. With the increase of the value of x from 0.3 to 0.7, the dielectric constant Εr and temperature coefficient of the resonance frequency τf increase, but the quality factor Q decreases. 0.5 Mg4Nb2O9/0.5 CaTiO3+1.7% V2O5 ceramics sintered at 1150C for 5 h have a relative dielectric constant Εr of 20, a Qf value of 48000 GHz (resonance frequency f=8 GHz) and a near zero τf value of -1210-6/°C.