Low-temperature Sintering Of Titanium Oxide Dielectric Ceramics

The low-temperature firing of TiO₂ ceramic was studied through the way of oxides addition. Effects of different oxides substitution on the density, microstructure and dielectric properties of TiO₂ ceramic were investigated systematically as well as the mechanisms of low-temperature firing. On the basis of low-temperature firing, the low-temperature co-firing properties of TiO₂ dielectric/NiZnCu ferrite multilayer composite were investigated. Main contents of this paper were as follows:In aspect of oxides addition, TiO₂ ceramic was first doped with CuO which could make the Ï„f of ceramics move towards negative direction. The mechanism of low-temperature firing was studied. Investigations revealed that CuO could reduce the sintering temperature of TiO₂ ceramics froml500°C to 950°C remarkably. The low-temperature firing of CuO-doped anatase was attributed to two mechanisms. Firstly, the addition of CuO to anatase samples resulted in lowering the temperature of the phase transformation from anatase to rutile as well as the temperature of the shrinkage anomaly. Secondly, the presence of a CuO-rich intergranular phase was observed, which indicates the presence of a liquid phase present at sintering temperatures. The low-temperature firing of B₂O₃-doped anatase mainly resulted from the low melting-point of B₂O₃ (450°C). Phase diagram between B₂O₃ and TiO₂ indicates that eutectic phase could be formed in low temperature which could accelerate the sintering.On the basis of single oxide addition, multiplex oxides of V₂O₅-CuO were added to TiO₂ ceramics. Studies revealed that V₂O₅-CuO could reduce the sintering temperature of TiO₂ to 900°C for V₂O₅ and CuO formed eutectic phase at very low temperature which could accelerate the sintering. Otherwise, the substitution of V⁵+ to Ti⁴+ was another important mechanism in lowering firing-temperature of TiO₂. Ion substitution resulted in the present of aberrance in TiO₂ crystal lattice as well as reducing the activation energy of diffusion.On the basis of low-firing of TiO₂, the low-temperature co-firing properties of TiO₂/NiZnCu ferrite multilayer composite was investigated. Problems such as camber in the interface were found for the different firing properties of them when they were co-fired together directly. The interlayer prepared by mixing TiO₂ dielectric and NiZnCu ferrite material was designed to solve the problems. The results showed that the interlayer could be co-fired with TiO₂ dielectric and NiZnCu ferrite material properly each, on the basis of which the three-layer co-firing of TiO2/interlayer/NiZnCu ferrite was achieved. The results showed that the ionic difference concentrations between the TiO₂ dielectric and NiZnCu ferrite material was reduced by interlayer, which weakened the diffusion of ion at the interface and diminished the crystal grain, the camber were not found yet at the same time.