Preparation and Microwave Dielectric Properties of Ultra-low Temperature Sintering Ceramics in K_2O-MoO_3 Binary System

摘要

A series of microwave dielectric ceramics in the compositions of K_2Mo_2O_7, K_2Mo_3O_(10), and K_2Mo_4O_(13) in K_2O-MoO_3 binary system with ultra low sintering temperatures were prepared using the solid-state reaction method. Their synthesis, phase composition, compatibility with metal electrodes, microstruc-tures, and microwave dielectric properties were investigated. The K_2MO_2O_7 ceramic sintered at 460℃ with a triclinic structure has a relative permittivity of 7.5, a Q × f value of 22 000 GHz, and a τ_f value of -63 ppm/℃. The X-ray diffraction patterns indicate that K_2Mo_2O_7 does not react with Ag and Al electrodes at the co-fired temperatures. The K_2Mo_3O_(10) ceramic can be sintered well at 520℃ with a relative permittivity of 5.6, a Q × f value of 35 830 GHz, and a τ_f value of -92 ppm/℃. It has compatibility with Ag electrode. The K_2Mo_4O_(13) ceramic sintered at 540℃ possesses good microwave dielectric properties with a relative permittivity of 6.8, a Q × f value of 39 290 GHz and a τ_f value of -67 ppm/℃ and it is compatible with AI electrode. For K_2Mo_2O_7 and K_2Mo_4O_(13), it is found that the grain sizes and the number of grain boundaries play an important role in the dielectric loss. From this study, it can be seen that the three ceramics in K_2O-MoO_3 system have good microwave dielectric properties, ultra-low sintering temperatures, non-toxic, and low-cost characteristics. So they can be potentially applied to ultra-LTCC devices.