Structural, thermal and microwave dielectric properties of the novel microwave material Ba₂TiGe₂O₈
Rapid developments of microwave dielectric materials have emerged in recent years due to their wide-spread applications and the revolution in wireless communications. However, many commercial microwave materials are based on titanates, niobates and tantalates which have the disadvantages both of costly raw materials and high sintering temperatures. These result in a production process which is not energy efficient. In this paper we develop a BaO-TiO₂-GeO₂ ternary system derived from the BaO-TiO₂ binary system to obtain low temperature co-fired microwave dielectric ceramics for high frequency applications. The Ba₂TiGe₂O₈ ceramics were prepared via the conventional solid-state route. The X-ray diffraction results showed that Ba₂TiGe2O₈ belongs to the orthorhombic, Cmm2 space group. The ceramics exhibited a densification of 96.3% after being sintered at 1060 °C. They also exhibited a relative permittivity (εr) of 12.7, a quality factor (Q×f) of 9060 GHz (at 10 GHz), a temperature coefficient of resonant frequency (τf) of −30 ppm/°C and a coefficient of thermal expansion (CTE) of 11.0 ppm/°C. In addition, the Raman spectra and ionic polarizability of Ba₂TiGe₂O₈ unit cells were investigated.