Formation Process and Microwave Dielectric Properties of the R_2V_2O_7 (R = Ba, Sr, and Ca) Ceramics

摘要

Formation process and microwave dielectric properties of the R_2V_2O_7 (R = Ba, Sr, and Ca) ceramics were investigated. Transient RV_2O_6 phases, which were formed at 300°～500℃ by the reaction of RCO_3 and V_2O_5, interacted with remnant RCO_3 to form the homogeneous triclinic R_2V_2O_7 phases at 600°-700℃. The Sr_2V_2O_7 and Ca_2V_2O_7 ceramics sintered at 1000° and 950℃, respectively, for 10 h showed a dense microstructure with the microwave dielectric properties of ε_r= 10.4-12.1, Q×f = 15200-19520 GHz, and ι_f = -30.9-34.8 ppm/℃. However, the Ba_2V_2O_7 ceramic was well sintered at 900℃ for 10 h and it showed the good microwave dielectric properties of ε_r= 10.1, Q ×f= 51630 GHz, and ι_f = -26.5 ppm/℃.