Microwave synthesis and sintering of Mg4Nb2O9 nanoceramics

Mg 4 Nb 2 O 9 nanopowders were prepared from MgO and Nb 2 O 5 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 Mg 4 Nb 2 O 9 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. Mg 4 Nb 2 O 9 ceramics sintered at a low temperature of 1,300 °C using microwave heating showed almost full density and excellent microwave dielectric properties (ε r = 12.9, Q × f = 174,200 GHz and τ f = −68).