Sintering, Microstructure, and Microwave Dielectric Properties of Ca 1+x V 2 O 6 Ceramics

Ca 1+x V 2 O 6 ( x = 0.25, 0.50, 0.75, 1.0) ceramics were synthesized via the conventional solid-state reaction method. The effects of calcium ion content on the phase composition, sintering, microstructure, and microwave properties were investigated. XRD analysis showed that in the three samples with x < 1, the CaV 2 O 6 phase and the Ca 2 V 2 O 7 phase were the main phase and the secondary phase, respectively. In the sample with x = 1, Ca 2 V 2 O 7 was the only crystalline phase. EDS analysis was consistent with the above results. The results of phase content showed that the increase in Ca 2+ ion content led to an increase in the Ca 2 V 2 O 7 phase and a decrease in the CaV 2 O 6 phase. The increase in the Ca 2 V 2 O 7 phase content led to an increase in the ε r value, but worsened the Q × f value. In addition, due to the relatively large τ f value of the Ca 2 V 2 O 7 phase, the increase in Ca ions also improved the τ f value of the ceramics. The Ca 2 V 2 O 6 sample sintered at 950°C for 4 h showed optimal microwave dielectric properties: ε r = 11.9, Q × f = 38,500 GHz (at 8.9 GHz), τ f = −31 ppm/°C.