Influence of Mg substitutions for Zn on the phase relation and microwave dielectric properties of (Zn_1-xMg_x)₃Nb ₂O₈ (x = 0.02-1.0) system

The effects of substituting Zn with Mg on the phase relation and microwave dielectric properties of Zn₃Nb₂O₈ ceramics were investigated in this study. X-ray diffraction patterns illustrate that the (_1-xMg_x)₃Nb₂O₈ solid solution could be formed in the composition range of x = 0-0.6, while the two phase regions with a mixture of MgNb₂O₆ and Mg ₄Nb₂O₉ were identified for x = 0.8-1.0. A small level of Mg substitution (x = 0.05) substantially improved the Q × f value of the ceramics. Either decreasing the A-site bond valence or increasing the B-site bond valence leads to a decrease in the sf value. An extremely low-loss dielectric can be achieved for specimens using (Zn0.95Mg0.05) ₃Nb₂O₈ ceramics (er ∼ 21.52, Q × f ∼ 130,000 GHz, sf ∼ -83.8 ppm/°C) after sintering at 1180 °C/4 h; consequently, it is proposed as a candidate material for high-frequency applications.