Structure, microwave dielectric performance, and infrared reflectivity spectrum of olivine-type Mg2Ge0.98O4 ceramic

An ultra-low dielectric loss ceramics Mg 2 Ge 0.98 O 4 with olivine structure was fabricated by conventional solid-state route. The phase composition, crystal structure, and microwave dielectric properties were investigated. The phase of Mg 2 Ge 0.98 O 4 is formed to the orthorhombic forsterite structure with a space group Pmnb (62). The dense microstructure and excellent microwave dielectric properties of Mg 2 Ge 0.98 O 4 ceramic were obtained at 1360°C for 4 hours, with relative density ~96.4%, ε r ~ 7.3, Q × f = 112 400 GHz, and τ f ~ −64.6 ppm/°C. The conductive mechanism of Mg 2 Ge 0.98 O 4 in the low frequency (<1 MHz) was studied by the dielectric spectroscopy and the result with E dc = 0.93 eV demonstrates that the defect was contributed to the double ionized oxygen vacancies. The intrinsic dielectric properties of Mg 2 Ge 0.98 O 4 in the microwave region were obtained by infrared reflectivity spectra with ε r ~ 7.13, Q × f = 120 400 GHz. And, acceptable τ f (~+2.6 ppm/°C) of 0.92Mg 2 Ge 0.98 O 4 –0.08CaTiO 3 composite ceramic was obtained by adding the CaTiO3.