(183af) Lattice Structure Analysis and Optimized Microwave Dielectric Properties of MgAl(2-2x)(Mg0.5Ti0.5)2xO4 Compounds with Spinel Structure

Dense MgAl_(2-2x)(Mg_0.5Ti_0.5)_2xO₄ ceramics with low permittivity were prepared by a standard solid-state reaction method. The single phase with spinel structure were achieved at x ≤ 0.10. Fd-3m space group was revealed by XRD, and the refined structure was analyzed by Rietveld analysis. Partial substitution of [Mg_0.5Ti_0.5]³⁺ for Al³⁺ could effectively reduce the densification temperatures and significantly improve dielectric constants and quality factor (Q×f) values compared to the MgAl₂O₄ ceramics. The increase in dielectric constant was attributed to the increasing normalized bond lengths of Al-O bonds and the higher polarizability of [Mg_0.5Ti_0.5]³⁺ than Al³⁺. In addition, the quality factor (Q×f) and temperature coefficient of resonant frequency (Ï„_f) were closely related to the cation disorder of the B-site characterized by the full width at half-maximum of E_g mode assigned to asymmetric bending of MgO₄ tetrahedra.