Effect of excess lithium on the structure and microwave dielectric properties of LiMg0.5Ti0.5O2 ceramics
Herein, Li 1+ x Mg 0.5 Ti 0.5 O 2 (0.000 ≤ x ≤ 0.075) ceramics with excess lithium were prepared by solid-state reaction method to compensate for lithium volatilization, thus optimizing dielectric properties. The second phase Mg 2 TiO 4 decreases with excess lithium content and eventually disappears at x = 0.05. Of these, Li 1.0375 Mg 0.5 Ti 0.5 O 2 illustrates the best dielectric properties with ε r = 16.58, Q × f = 120712 GHz (@9.18 GHz), and τ f = −16.31 ppm/°C. From the point of view of non-intrinsic factors, excess lithium at optimum ratios slightly facilitates the sintering of the ceramics, improves densification, and increases the grain size, resulting in improved dielectric properties. For intrinsic factors, a slight increase in bond ionicity results in a slight improvement in ε r . First-principles calculations demonstrate that suitable excess lithium increases electron cloud density in the internal space of Li/Mg/TiO 6 octahedron and increases band gap, thus optimizing the dielectric properties. The same results were obtained from the perspective of lattice vibrations. The modified Li 1.0375 Mg 0.5 Ti 0.5 O 2 ceramics offer great potential for future microwave communication technology.
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