NiNb2O6 ceramics with 8–10 mol% TiO2 were investigated. A mixture of raw materials was sintered into
ceramics by bypassing calcination and subsequent pulverization stages. The addition of TiO2 resulted in
the formation of a Ni4Nb2O9 phase and phases with the same structure as that of a Ni0.5Ti0.5NbO4 phase.
An increase in the TiO2 content resulted in an increase in the content of the Ni0.5Ti0.5NbO4-like phase,
especially at high sintering temperatures. The dielectric constant increased from29.2 at 1170 ◦C to 31.1 at
1230 ◦C in NiNb2O6 ceramics with 9 mol% TiO2. Qxf reached 36800GHz in NiNb2O6 ceramics with 8 mol%
TiO2. It decreased as the TiO2 content increased with the content of the Ni0.5Ti0.5NbO4-like phase with a
low Qxf. f between −2 and 2 ppm/◦C could be obtained in NiNb2O6 ceramics with 9 and 10 mol% TiO2.
Journal of Alloys and Compounds 477 (2009) 537–542