Influence of Sn4+ substitution for Si4+ on the microwave dielectric properties of Mg2Al4Si5−xSnxO18 ceramics

The Mg2Al4 Si 5 − x Snx O 1 8 ( 0 ≤ x ≤ 0 . 2 0 ) ceramics were successfully synthesized via the solid-state reaction method. The XRD results show that the main phase of the ceramics is Mg2Al4Si5 O 1 8 . When x = 0 , there is a second phase of Al2SiO5. With the increase of x, the content of Sn 2 + gradually increased, the Al2SiO5 phase disappeared, and the SnO2 and MgAl2O4 phases appeared. In addition, the cell volume of the ceramic changes with the increase of x, which indicates that partial Sn 2 + successfully enters the lattice with ion substitution and lattice distortion. The relative density and ε r are highly correlated. The quality factor (Qf) is not only affected by the relative density but also by the symmetry of the [Si4Al2] ring. The bond strength as an evaluation of the stability of the crystal structure determines the magnitude of τ f . Good microwave dielectric properties were achieved for samples at x = 0 . 0 4 with sintering at 1400∘C: ε r = 4 . 8 6 , Qf = 1 7 , 0 0 0 GHz and τ f = − 3 2 ppm/∘C, demonstrating that Mg2Al4 Si 4 . 9 6 Sn 0 . 0 4 O 1 8 ceramics are an ideal candidate for microwave electronics.