Phase composition, microstructure and microwave dielectric properties of rock salt structured Li2ZrO3-MgO ceramics

A novel series of rock salt structured (1-x)Li2ZrO3-xMgO ceramics were prepared via the conventional solid state method. The tetragonal-cubic phase transition can be observed in the case of 0.5 <= x <= 0.6, which has been testified by the results of XRD and SEM-EDS. Relatively dense and homogeneous microstructure can be obtained for all the compositions sintered at 1500 degrees C. With the x value increasing from 0.5 to 0.8, the relative permittivity linearly decreases from 16.50 to 12.65, and the tau(f) value decreases from similar to -10 ppm/degrees C to similar to -35 ppm/degrees C. The addition of MgO stabilizes the crystal structure and increases the bond energies in Li2ZrO3-MgO system, so there is an upward tendency in Q.f values from similar to 77,000 GHz to similar to 166,000 GHz. Typically, the Li2Mg4ZrO7 ceramics sintered at 1500 degrees C possesses excellent properties with epsilon(r) = 12.65, Q.f = 165,924 GHz and tau(f) = -34.66 ppm/degrees C, which makes these materials good candidates for microwave devices.