Influence of Mg substitutions for Zn on the phase relation and microwave dielectric properties of (Zn1−xMgx)3Nb2O8 (x = 0.02–1.0) system

• The (Zn1−xMgx)3Nb2O8 solid solutions for x = 0–0.6 were confirmed by the XRD.
• Measured lattice parameters, cell volume, and polarizability were investigated.
• Mg substitution for Zn produced a tremendous increase in Q × f value.
• The f value was associated with A- and B-site bond valence.

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 (Zn1−xMgx)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 Mg4Nb2O9 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 τf value. An extremely low-loss dielectric can be achieved for specimens using (Zn0.95Mg0.05)3Nb2O8 ceramics (εr ∼ 21.52, Q × f ∼ 130,000 GHz, τf ∼ –83.8 ppm/°C) after sintering at 1180 °C/4 h; consequently, it is proposed as a candidate material for high-frequency applications.