Synthesis and microwave dielectric properties of columbite-structure MgNb2O6 ceramics by aqueous sol–gel technique

Columbite-type MgNb2O6 ceramics were prepared by aqueous sol–gel method and their microwave dielectric properties were investigated. Firstly, highly reactive nanosized MgNb2O6 powders were successfully synthesized at 500 °C in oxygen atmosphere with particle size of 20–40 nm. Phase formation was detected by DTA-TG and XRD. Subsequently, Sintering characteristics and microwave dielectric properties of MgNb2O6 ceramics were studied at different temperatures ranging from 1050 °C to 1250 °C. With the increase of sintering temperature, density, er and Q × ƒ values increased and saturated at 1150 °C with excellent microwave properties of e r = 18.7, Q × ƒ = 90,700 GHz and τ ƒ = −48.5 ppm/°C. These results showed that the sintering temperature of MgNb2O6 ceramics was significantly reduced by aqueous sol–gel process.