Microwave synthesis and sintering of Mg4Nb2O9 nanoceramics

Mg4Nb2O9 nanopowders were prepared from MgO and Nb2O5 mixtures by using a high energy ball milling method, combined with subsequent annealing at low temperatures by microwave heating. After milling for 20 h, pure phase Mg4Nb2O9 nanopowders with an average grain size of 127 nm were obtained at 850, 130 °C lower than that required by a conventional solid state reaction process. Mg4Nb2O9 ceramics sintered at a low temperature of 1,300 °C using microwave heating showed almost full density and excellent microwave dielectric properties (εr = 12.9, Q × f = 174,200 GHz and τf = −68).