Lossy Titanite-Based Ceramics with Nominal Compositions CaTi_1-xM_ySiO ₅ (0 ≦ X, Y ≦ 1, M = Mn, Sn, Zr, Nb) Applicable to Millimeter Electromagnetic Wave Absorber

Abstract:

The titanite-based ceramics with nominal composition CaTi_1-xM_ySiO₅ (0≦x≦1, M = Mn, Sn, Zr (y = x), and M = Nb (y = 4x/5)) in which part x of Ti sites are replaced by several kinds of atoms had remarkable increase in both the real and imaginary parts of complex relative permittivity around x = 0.0125~0.1 compared with those of pure titanite CaTiSiO₅ ( x = 0) at 70 GHz. Real part varied from 3 to 43, and the imaginary part from 0 to 12 (tangent delta from 0 to 0.28). No reflection condition is fulfilled for M = Zr when x = 0.05, d/λ₀ =0.042, and for M = Nb in both cases when 0 < x < 0.0125, d/λ₀ = 0.05 and 0.1 <x < 0.2, d/λ₀ =0.042, where d is thickness of the plate sample and λ₀ is the wavelength of incident electromagnetic wave. The dominant dielectric dispersion may occur due to difference of ionic polarization between Ti⁴⁺ ions and Mn⁴⁺, Sn⁴⁺, Zr⁴⁺, or Nb⁵⁺ ions relative to O^2- ions, which becomes inactive and saturates around x = 0.0125~0.05. From the measurement of the lattice parameters, a, b, c, and the angle β, characterizing monoclinic crystal structure, this saturation may have close correlation with some structural rearrangement of constituting atoms, Ti and substituted M atoms in CaTi_1-xM_ySiO₅

• Periodical: Key Engineering Materials (Volume 888)
• Pages: 9-14
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.888.9
• Online since: June 2021
• Authors: Yutaka Higashida*, Minato Ando
• Keywords: Complex Relative Permittivity, Electromagnetic Wave Absorber, Millimeter Wave, Titanite

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