Low-temperature firing and microwave dielectric properties of BaTi₄O₉ with Zn-B-O glass system

The effect of Zn-B-O (ZB) glass additions on the sintering temperature and microwave dielectric properties of BaTi₄O₉ has been investigated using X-ray diffraction, scanning electron microscopy, dilatometry and electrical characterization. It was found that the addition of small amount of glass to BaTi₄O₉ lowered the sintering temperature to ∼900°C while maintaining good microwave properties. In sintered samples with ZB glass, plate-like abnormal grains (∼5 μm) were observed. ZB glass heat-treated at 900°C for 2 h was crystallized to Zn(BO₂)₂ and Zn₃(BO₃)₂, which coincides with second phases detected in low-temperature fired BaTi₄O₉. Thus it can be concluded that there is a negligible reaction forming other second phases between BaTi₄O₉ and ZB glass. BaTi₄O₉ ceramics sintered at 900°C for 2 h had good microwave dielectric properties: relative dielectric constant (ε_r) = 33, quality factor (Qxf) = 27000, and temperature coefficient of resonant frequency (τ_f) = 7 ppm/°C.