Effect of nonstoichiometry on the structure and microwave dielectric properties of Ba(Co1/3Nb2/3)O3 ceramics

The effect of B-site cation deficiency on the structure and microwave dielectric properties of Ba(Co1/3Nb2/3)O3 (BCN) was investigated. Stoichiometric and co-deficient compositions based on Ba(Co1/3−xNb2/3)O3 [x = 0.0, 0.01, 0.02, 0.03 and 0.04] were prepared using the conventional mixed oxide route. Small amounts of V2O5 (0.1 wt%) were added to promote densification. The dielectric loss is very sensitive to the composition; it was found that co-deficiency degraded the microwave dielectric properties. The stoichiometric formulation (x = 0) exhibited the best microwave properties. The improvements in the microwave dielectric properties were achieved by increasing the degree of 1:2 cation ordering. The highly ordered, stoichiometric BCN ceramics showed a relative permittivity (ɛr) of 32, quality factor (Q × f) of 66,500 GHz and a negative temperature coefficient of resonant frequency (τf) of −10 ppm/°C at 4 GHz.