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: εr = 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. εr around 45, Q×f = 5400–7700 GHz (at 6 GHz) and τf ∼73 ppm/◦C
were obtained in pellets with 30 mol% TiO2 addition. εr around 50, Q×f = 3800–5700 GHz (at 6 GHz) and τf ∼99 ppm/◦C were obtained in pellets
with 40 mol% TiO2 addition.
Journal of the European Ceramic Society 29 (2009) 1165–1171