Microwave dielectric properties of BaO–TiO2–TeO2 ternary system

Besides the applications as optical functional materials, tellurium oxides also have attracted interest as microwave dielectric materials. Most TeO2-based binary and ternary system have large negative temperature coefficient of resonant frequency (τf), which is not compatible for the low-temperature cofired ceramic. To compensate τf close to zero, two single-phase predecessors of BaTe4O9 and TiTe3O8 are synthesized in air at 530–560 and 620–680 °C, respectively. The two predecessors show exceptional dielectric properties and their τf are opposite. The BaO–TiO2–TeO2 ternary system compounds are investigated by adjusting the ratio of BaTe4O9 and TiTe3O8 and sintered at 520–580 °C to develop the microwave properties and compensate the τf. After sintered at 560 °C, the ceramic sample with the composition of 0.47BaTe4O9–0.53TiTe3O8 exhibits a dielectric permittivity of 28, a Q × f-value of 12,200 GHz, and a τf of 4.0 ppm/°C measured at 10 GHz.