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

Formation process and microwave dielectric properties of the R 2 V 2 O 7 (R=Ba, Sr, and Ca) ceramics were investigated. Transient RV 2 O 6 phases, which were formed at 300°∼500°C by the reaction of RCO 3 and V 2 O 5 , interacted with remnant RCO 3 to form the homogeneous triclinic R 2 V 2 O 7 phases at 600°–700°C. The Sr 2 V 2 O 7 and Ca 2 V 2 O 7 ceramics sintered at 1000° and 950°C, respectively, for 10 h showed a dense microstructure with the microwave dielectric properties of ɛ r =10.4–12.1, Q × f =15 200–19 520 GHz, and τ f =−30.9–34.8 ppm/°C. However, the Ba 2 V 2 O 7 ceramic was well sintered at 900°C for 10 h and it showed the good microwave dielectric properties of ɛ r =10.1, Q × f =51 630 GHz, and τ f =−26.5 ppm/°C.