Structure and microwave dielectric properties of (Zn1-xNix )TiO3 ceramics

Dielectric ceramics in the system (Zn1-xNix)TiO3, X = 0 to 1 were synthesized by the solid-state reaction route. The phase distribution, microstructure, and dielectric properties were characterized using powder x-ray diffraction analysis, electron microscopy, and microwave measurement techniques. Three phase composition regions were identified in the specimens sintered at 1150 degreesC: [spinet + rutile] at 0 less than or equal to x less than or equal to 0.5, [spinet + ilmenite + rutile] at 0.5 < x less than or equal to 0.8, and [ilmenite] phase at 0.8 < x less than or equal to 1. For the 0 less than or equal to x less than or equal to 0.5 region, the amount of Ti-rich precipitates incorporated into the spinel phase decreased with the Ni content at 0 less than or equal to x less than or equal to 0.5, with a concomitant increase of the rutile phase. The microwave dielectric properties depended on the phase composition and volume according to the three typical phase regions, where the relative amount of rutile to the spinet or ilmenite determined the dielectric properties. The dielectric constant as a function of Ni addition was modeled with a Maxwell mixing rule. An optimum phase distribution was determined in this system with dielectric constant of 22, a Q x f of 60,000, and a low temperature coefficient of the resonant frequency.