Crystal structure and microwave dielectric properties of CaTiO3 modified Mg2Al4Si5O18 cordierite ceramics

In this work, CaTiO3 modified Mg2Al4Si5O18 (MAS) of (1 - x)MAS-xCaTiO(3) (0 <= x <= 0.35) cordierite ceramics were fabricated by traditional solid phase sintering method. The densification sintering temperatures of (1 - x)MAS-xCaTiO(3) ceramics are effectively lowered from 1460 degrees C to 1250 degrees C with increasing addition of CaTiO3. X- ray diffraction spectra show that (1 - x)MAS-xCaTiO(3) ceramics present cordierite phase as 0 < x <= 0.05, and the composite phases of cordierite, perovskite- structured CaTiO3 and monoclinic feldspar phase of CaAl2Si2O8 as 0.10 <= x <= 0.35. Rietveld refinement of XRD data show the six- membered rings of [(Si4Al2)O-18] transit from non-symmetry rings to centro- symmetry equilateral rings in (1 - x)MAS-xCaTiO(3) (0 < x <= 0.10). The optimal dielectric properties of Q x f = 55490 GHz (at 15.3 GHz), epsilon(r) = 7.2 and tau(f) = -28.3 ppm/degrees C are obtained at x = 0.5, which are better than those of pure MAS cordierite ceramics. (C) 2016 Elsevier B.V. All rights reserved.