Lattice structure analysis and optimised microwave dielectric properties of LiAl1-x(Zn0.5Si0.5)xO2 solid solutions

Low-permittivity LiAl_1-x(Zn_0.5Si_0.5)_xO₂ microwave dielectric ceramics were prepared by the solid-state reaction method. Single-phase LiAlO₂ solid solutions with a tetragonal structure were achieved at x ≤ 0.12. Partial substitution of Zn_0.5Si_0.5]³⁺ for Al³⁺ could improve the microstructure and prevent from absorbing moisture of pure LiAlO₂ ceramics, which slightly increases their relative permittivity (ε_r). The quality factor (Q × f) and temperature coefficient of resonant frequency (τ_f) were closely related to the crystallinity and cation disorder of the B-site characterized by the full width at half-maximum of B₁⁽¹⁾ –mode assigned to Li–O–Al stretching. The optimum microwave dielectric properties (ε_r = 6.12, Q × f = 56986 GHz and τ_f = -122 ppm/°C) were obtained in the sample with x = 0.02 sintered at 1300 °C.