Relationship between chemical bond characteristics and microwave dielectric properties of low temperature sintering CoO-V2O5 ceramics

Abstract

The two most fundamental compositions within the CoO-V2O5 family, namely CoV2O6 and Co2V2O7 ceramics, were synthesized using the traditional solid-state method. The microwave dielectric properties of both ceramics were investigated for the first time. The P-V-L bond theory was used to analyze the correlation between their microwave dielectric properties and chemical bond characteristics. The CoV2O6 ceramic exhibits a γ phase (εr = 11.6, Q×f = 39,177 GHz, and τf = −15 ppm/°C) when sintered at 660 °C. However, it experiences a phase transformation from the γ phase to the α phase at 690 °C, which causes the dielectric properties to degrade. The Co2V2O7 ceramic demonstrates excellent dielectric characteristics (εr = 9.4, Q×f = 88,645 GHz, and τf = −37 ppm/°C) at 720 °C. Importantly, its sintering temperature can be lowered to 660 °C while still maintaining a good combination of microwave dielectric properties (εr = 7.7, Q×f = 75,887 GHz, and τf = −58 ppm/°C). It is found that Co2V2O7 exhibits a low dielectric loss due to relatively high lattice energy resulting from the contribution of Co–O bonds. CoV2O6, on the other hand, shows a lower sintering temperature because it contains more V2O5, which acts as an effective sintering aid. These two ceramics both exhibit good chemical compatibility with aluminum and are promising candidates for applications in low-temperature and ultra-low-temperature co-fired ceramics (LTCCs and ULTCCs) that operate in the microwave frequency range or higher.