Enhanced dielectric properties of ternary ZnO-based composites for dielectric applications

In this work, (1-x) ZnO/xNb₂O₅ mixture with (x = 0.01, 0.05, 0.1, 0.15 and 0.2) is used to synthesize composites by means of the solid-state method. The X-ray analysis affirms the formation of ZnO/ZnNb₂O₆ binary composite for x = 0.01, while ZnO/ZnNb₂O₆/Nb₂O₅ ternary composite was formed from x = 0.05. The morphological distribution confirms that the average grain size increases with the increase of Nb₂O₅ percent. Moreover, the dielectric and electric properties of the composites are investigated using impedance spectroscopy and van der Pauw method. In fact, using the theoretical adjustment of the curve the material is modeled with an equivalent electric circuit including two parallel combinations of resistance and fractal capacitance, related to grains and grain boundary contributions. This study demonstrates the enhancement of the grain boundary contributions in the composites compared to ZnO, and high resistive and capacitive behavior. Moreover, the composites have lower loss factor than ZnO. Furthermore, it can be seen that the dielectric properties of the composites are changed as a function of Nb₂O₅ percentage. The 10% composite presents low resistance, high charge carrier’s concentration and high mobility, high permittivity and important capacitive behavior. For higher percent (≥ 15 mol%), the composites become more resistive with low mobility and low charge carrier’s concentration, high permittivity and a capacitive behavior. The enhancement in the dielectric properties with increasing Nb₂O₅ concentration suggests that these composites are useful for various dielectric device applications. In addition, the magnetic analysis demonstrates that from x = 0.1 the composite exhibits ferromagnetic behavior at room temperature.