Origin of Microwave Dielectric Loss in ZnNb 2 O 6 ‐TiO 2

(1− x )ZnNb 2 O 6 · x TiO 2 ceramics were prepared using both anatase and rutile forms of TiO 2 . At a composition of x = 0.58, a mixture region of ixiolite (ZnTiNb 2 O 8 ) and rutile was observed and the temperature coefficient of resonant frequency (τ f ) was ∼0 ppm/°C. We found that although ɛ r and τ f were comparable, the quality factor ( Q × f , Q ≈ 1/ tan δ, f = resonant frequency) of 0.42ZnNb 2 O 6 ·0.58TiO 2 prepared from anatase and rutile was 6000 and 29 000, respectively. The origin of the difference in Q × f of both samples was investigated by measuring electrical conductivity and by analysis of the anatase–rutile phase transition. The anatase‐derived sample had higher conductivity, which was related to the reduction of Ti 4+ . It is suggested that the increase of dielectric loss originates from an increase in Ti 3+ and oxygen vacancies due to an anatase–rutile phase transition.