Correlations between microwave dielectric properties and crystal structures of Sb-doped Co0.5Ti0.5NbO4 ceramics

Co 0.5 Ti 0.5 Nb 1- x Sb x O 4 ( x  = 0, 0.1, 0.2, 0.3, 0.4, 0.5) ceramics with low dielectric losses were fabricated by the conventional solid-state reaction method. A single-phase tetragonal rutile structure with a superlattice diffraction peak was observed. The temperature coefficient of resonant frequency ( τ f ) decreased with an increase in oxygen octahedron distortion. The quality factor ( Q × f ) was increased owing to the enhanced cation ordering, which reduced the lattice energy and internal stress of the oxygen octahedron. Sb 3+ was transformed into Sb 5+ , while the transformation of Co 2+ to Co 3+ was inhibited. The as-prepared Co 0.5 Ti 0.5 Nb 0.5 Sb 0.5 O 4 ceramic exhibited ε r of 38, Q   ×   f of 32,047 GHz, and τ f of 32.6 parts-per-million/°C.