Enhanced microwave dielectric and electrical properties of Zn substituted Mg₂TiO₄ ceramics for RF/microwave applications

The structural, microstructural, electrical and microwave dielectric properties of Mg₂Ti_1−xZn_xO₄ (x = 0.01–0.05) ceramics prepared by solid-state reaction method have been reported. The X-ray diffraction patterns and Raman spectra have showed the presence of pure Mg₂TiO₄ (MMTO) along with some fraction of MgTiO₃ (MTO) phase. It is observed that the cubic structure of MMTO is deformed and evaluated to become pseudo cubic structure with Zn substitution. The surface morphology of the sintered MMTO ceramics at 1350 °C exhibited uniform and dense microstructures. Temperature dependent dielectric response of Mg₂Ti_1−xO₄Zn_x ceramics with x = 0.03, showed stable dielectric response in the temperature range from RT to 300 °C. The overall enhancement in dielectric response of the samples is attributed to the compositional heterogeneity due to substitution of Zn²⁺ in the Ti⁴⁺ site. The complex impedance spectra revealed two parallel RC combination circuit [(R_gC_g) (R_gbC_gb)] elements in series. The dispersion of AC conductivity followed Jonscher’s power law, and non-overlapping small polaron hole hopping assisted conductivity. Mg₂Ti_1−xZn_xO₄ ceramics with x = 0.03, exhibited best structural, dielectric and microwave dielectric property with uniform and dense microstructure, moderate dielectric constant (ε_r) ~ 23 and quality factor (Q × f_o) ~ 165 THz at 8.89 GHz. A voltage independent capacitance for the sample at all the measured frequencies have observed. The obtained properties of the ceramics are promising for dielectric resonator, microwave integrated circuit and type-I capacitor applications.