Synthesis and properties of TiO2 added NiNb2O6 microwave dielectric ceramics using a simple process

TiO2 added NiNb2O6 ceramics produced using a reaction-sintering process were investigated. Pure columbite NiNb2O6 could be obtained without TiO2 addition. With 30 and 40 mol% TiO2 addition, a phase with the same structure of Ni0.5Ti0.5NbO4 formed. Grain growth is easier in pellets with 30 and 40 mol% TiO2 addition than in the NiNb2O6 pellets. Microwave dielectric properties: ɛr = 20.7, Q × f = 19,800 GHz (at 9 GHz) and τf = −31.9 ppm/°C were obtained for NiNb2O6 pellets sintered at 1300 °C/2 h. ɛr around 45, Q × f = 5400–7700 GHz (at 6 GHz) and τf ∼ 73 ppm/°C were obtained in pellets with 30 mol% TiO2 addition. ɛr around 50, Q × f = 3800–5700 GHz (at 6 GHz) and τf ∼ 99 ppm/°C were obtained in pellets with 40 mol% TiO2 addition.