Formation Process and Microwave Dielectric Properties of the R2V2O7 (R=Ba, Sr, and Ca) Ceramics

Formation process and microwave dielectric properties of the R2V2O7 (R=Ba, Sr, and Ca) ceramics were investigated. Transient RV2O6 phases, which were formed at 300°∼500°C by the reaction of RCO3 and V2O5, interacted with remnant RCO3 to form the homogeneous triclinic R2V2O7 phases at 600°–700°C. The Sr2V2O7 and Ca2V2O7 ceramics sintered at 1000° and 950°C, respectively, for 10 h showed a dense microstructure with the microwave dielectric properties of ɛr=10.4–12.1, Q×f=15 200–19 520 GHz, and τf=−30.9–34.8 ppm/°C. However, the Ba2V2O7 ceramic was well sintered at 900°C for 10 h and it showed the good microwave dielectric properties of ɛr=10.1, Q×f=51 630 GHz, and τf=−26.5 ppm/°C.