Structure, microwave dielectric performance, and infrared reflectivity spectrum of olivine‐type Mg₂Ge_0.98O₄ ceramic

Abstract

An ultra‐low dielectric loss ceramics Mg2Ge0.98O4 with olivine structure was fabricated by conventional solid‐state route. The phase composition, crystal structure, and microwave dielectric properties were investigated. The phase of Mg2Ge0.98O4 is formed to the orthorhombic forsterite structure with a space group Pmnb (62). The dense microstructure and excellent microwave dielectric properties of Mg2Ge0.98O4 ceramic were obtained at 1360°C for 4 hours, with relative density ~96.4%, εr ~ 7.3, Q × f = 112 400 GHz, and τf ~ −64.6 ppm/°C. The conductive mechanism of Mg2Ge0.98O4 in the low frequency (<1 MHz) was studied by the dielectric spectroscopy and the result with Edc = 0.93 eV demonstrates that the defect was contributed to the double ionized oxygen vacancies. The intrinsic dielectric properties of Mg2Ge0.98O4 in the microwave region were obtained by infrared reflectivity spectra with εr ~ 7.13, Q × f = 120 400 GHz. And, acceptable τf (~+2.6 ppm/°C) of 0.92Mg2Ge0.98O4–0.08CaTiO3 composite ceramic was obtained by adding the CaTiO3.

Ni–Co Complex Ionic Synergistically Modifying Octahedron Lattice of Cordierite Ceramics for the Application of 5G Microwave–Millimeter-wave Antennas

“…Subsequently, the contribution of the lattice vibration to the microwave dielectric properties was calculated and evaluated through the Kramers−Kronig (K−K) relationship. 39 The formulas for the dielectric response relationship, detailed in S1−S4 (Supporting Information), were compared with the complex dielectric spectrum obtained from down-conversion in the terahertz frequency band. Figure 8a shows that the measured far-infrared reflectance value of the Mg 1.8 (Ni x Co 1−x ) 0.2 Al 4 Si 5 O 18 (x = 0.5) ceramic sample is consistent with the fitted value.…”

Phase composition, crystal structure, and microwave dielectric properties of LiIn1‐xAlxO2 ceramics

“…To better understand the influence of TA B L E 1 The unit cell data (a, c, and 𝑣 𝑚 ) calculated from the XRD patterns, trial, theoretical and corrected dielectric constant (ε r, ε th, and ε corr ) of LiIn Al 3+ substitution for In 3+ on the permittivity (ε r ), the theoretical permittivity (ε th = 9.77) of LiIn0 .95 Al0 .05 O 2 ceramic was first calculated according to the Clausius-Mossotti equation (see Supporting Information). 23 And then its porosity corrected permittivity (ε cor = 14.74) is obtained based on the following equation 24 :…”

“…With the x increasing, the ε r (maximum values for each composition) from 9.6 ( x = 0) increases to 13.5 ( x = 0.15) and then slightly decreased to 11.2. To better understand the influence of Al 3+ substitution for In 3+ on the permittivity ( ε r ), the theoretical permittivity ( ε th = 9.77) of LiIn0 .95 Al0 .05 O 2 ceramic was first calculated according to the Clausius–Mossotti equation (see Supporting Information) 23 . And then its porosity corrected permittivity ( ε cor = 14.74) is obtained based on the following equation 24 : $$$$\begin{equation}\ \varepsilon ^{\prime} = {\varepsilon }_m\ \left( {1 - \frac{{3P\left( {{\varepsilon }_m - 1} \right)}}{{2{\varepsilon }_m + 1}}} \right).\end{equation}$$$$…”

Low permittivity cordierite-based microwave dielectric ceramics for 5G/6G telecommunications

“…εr in the THz band is smaller than that at microwave frequencies, which is attributed to intrinsic factors such as dipoles and lattice vibrations. The intrinsic microwave dielectric properties of MAS-Tx (x=0, 1.5, 5.5) ceramics were further investigated by infrared reflectance, and the results analyzed using a classical harmonic model [43][44][45][46][47] :…”