Abstract
In this work, the MgAl2-x(Cu0.5Ti0.5)xO4 (x = 0, 0.04, 0.08, 0.12, 0.16, and 0.20) ceramic system was synthesized using the solid-state route. The crystalline phases, crystal structure,and microwave dielectric properties of the samples were investigated. The XRD data presented a typical spinel structure of MgAl2O4 and was processed using the Rietveld refinement method. TiO2, Al2TiO5 and MgTi2O5 were considered as secondary phases. SEM indicated that the densification was affected by the (Cu0.5Ti0.5)3+ content and sintering temperature. The successful fabrication of MgAl2-x(Cu0.5Ti0.5)xO4 and the presence of MgTi2O5 were confirmed by EDS. The densification, secondary phases and cation vacancies were responsible for the variation of Qf values. The εr values were dominated by secondary phases and ionic polarizability. Meanwhile, secondary phases and bond valence had a significant influence on the τf values. The optimum microwave dielectric properties (Qf = 42,036 GHz, εr = 8.72 and τf = -5.0 ppm/°C) were obtained. Temperature stability was improved by 93.8% when compared to pure MgAl2O4 (τf = -80.0 ppm/°C). The as-prepared ceramics possess low transmission delay time, high temperature stability, preferable frequency selective characteristics, and low dielectric loss.
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