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 °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 τf value decreases from ∼−10 ppm/°C to ∼−35 ppm/°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 ∼77,000 GHz to ∼166,000 GHz. Typically, the Li2Mg4ZrO7 ceramics sintered at 1500 °C possesses excellent properties with εr = 12.65, Q·f = 165,924 GHz and τf=-34.66 ppm/°C, which makes these materials good candidates for microwave devices.