LOW-TEMPERATURE SINTERING OF V2O5-ADDED AND -SUBSTITUTED ZnNb2O6 MICROWAVE CERAMICS

The sintering behaviors and microwave dielectric properties of V2O5-added and -substituted ZnNb2O6 ceramics with columbite structure (abbreviated as ZNV and ZVN, respectively) have been investigated. It was found that the addition or substitution of V2O5 to ZnNb2O6 ceramics lowers the sintering temperature from 1150 C to approximately equals 900 C, but the sintering mechanisms are different. The formation of a ternary liquid phase is attributed to enhanced sintering in ZNV samples. Interaction between ZnNb2O6 and V2O5 also led to the formation of a second phase, V3Nb17O50. In contrast, it has been observed that with up to 8 mol% substitution of V2O5 in ZnNb2O6, a complete solid solution is formed. The sintering temperature for the ZVN sample becomes lower due to the decreased temperature of liquidus according to the substitution of V for Nb ions. The microwave dielectric properties of ZNV samples are seriously degraded due to the presence of a V3Nb17O50 second phase. This was confirmed by measuring the dielectric properties of V3Nb17O50 second phase. However, V-substituted Zn(Nb0.94V0.06)2O6 samples sintered at 875 C for 2 h exhibit excellent microwave dielectric properties. 20 refs.