The addition of B2O3 to Ba5Nb4O15-BaNb2O6 significantly lowered the sintering temperature to ∼900 °C in comparison to ∼1250 °C for samples without B2O3. The presence of a B2O3-rich intergranular phase in the sample was observed, which was attributed to the presence of a liquid phase during sintering. The barium metaniobate, BaNb2O6 has two polymorphs, with orthorhombic and hexagonal forms. A major contributor to microwave dielectric properties of low-fired samples is the low temperature phase, hexagonal BaNb2O6. The small amount of hexagonal BaNb2O6 could tune τf of Ba5Nb4O15. Therefore, Ba5Nb4O15-BaNb2O6 with B2O3 can be a suitable for low-temperature cofired ceramic (LTCC), due to its reduced sintering temperature and good microwave dielectric properties: Q×f = 28 000 GHz, εr and τf are 42 and 0 ppm/°C, respectively. The chemical compatibility of silver electrodes and low-fired samples has also been investigated.
- Dielectric properties
- Electron microscopy