Effects of barium ions non-stoichiometry on the microstructure and microwave properties of BaCo2V2O8 ceramics

The effects of barium ions non-stoichiometry on the phase composition, microstructure, and microwave properties of Ba 1+x Co 2 V 2 O 8 (x = 0–0.5) ceramics were studied. XRD results show that the single phase of BaCo 2 V 2 O 8 was found in the composition of x equal to zero while a secondary phase of Ba 2 V 2 O 7 started to precipitate at 0.5 ≥ x ≥ 0.2, as confirmed by SEM and EDX. The appearance of Ba 2 V 2 O 7 phase with higher sintering temperature is the main reason of the increase of the optimum sintering temperature of the system. The comparisons between theoretical and experimental values of microwave dielectric properties indicate that the appearance of second phase (Ba 2 V 2 O 7 ) leads to the decrease of dielectric constant and the improvement of the temperature coefficient of frequency and the quality factor values. Ba 1.5 Co 2 V 2 O 8 ceramic sintered at 925 °C showed good properties: ε r  = 11.5, Q   ×  f  = 47,230 GHz and τ f  = − 32.1 ppm/°C.