ZnTiO3 Phase Research Articles

Phase transitions of low-temperature sintering tungsten-doped ZnO-TiO2 ceramics

WO3-doped zinc titanate ceramics were prepared by conventional mixed-oxide method combined with a chemical processing. The effects of WO3 addition on the low-temperature sintering behavior, phase transition and dielectric properties of zinc titanate ceramics were investigated. The results show that the densification temperature of ZnTiO3 ceramics can be reduced from 1150 to 900 °C with WO3 addition and chemical processing. Small amount of WO3 (<1.00wt %) accelerated the decomposition of hexagonal ZnTiO3 phase to cubic Zn2TiO4 phase, while excessive addition (for example, 3.00wt %) restrained the decomposition. At the same time, the phase transition temperature from hexagonal ZnTiO3 phase to cubic Zn2TiO4 is lowered by adding WO3. WO3 addition affects the dielectric properties of ceramics. The dielectric properties of WO3-doped zinc titanate ceramics were measured at different frequencies. The results showed the decreasing tendency with the increasing measuring frequencies for both the dielectric constants and the loss tangents, and there existed the best dielectric properties for 1.0% WO3-doped ceramics.

Effects of V2O5 addition on the phase-structure and dielectric properties of zinc titanate ceramics

V2O5-doped zinc titanate ceramics (ZnTiO3) were prepared by conventional mixed-oxide method combined with a semi-chemical processing. The effects of V2O5 addition on the phase-structures and the dielectric properties of ZnTiO3 ceramics were investigated. The results show the sintering temperature of zinc titanate ceramics could be lowered from 1,150 to 930 °C by reducing the size of starting powders using a semi-chemical processing; and with adding V2O5 addition, the densification temperature of ZnTiO3 ceramics could be reduced to 875 °C. Also the phase transition temperature from hexagonal ZnTiO3 phase to cubic Zn2TiO4 was lowered by adding V2O5. The best properties were: ɛ r = 20.6, \( Q \times f = 8,873\;{\text{GHz}} \), when the ceramics was sintered at 900 °C, which is a promising candidate in the field of multi-layer devices requiring low sintering temperature (≤900 °C).

Effect of Inner Electrode on Reliability of (Zn,Mg)TiO3-Based Multilayer Ceramic Capacitor

In this study, different proportions of silver-palladium alloy acting as the inner electrode were adopted to a (Zn,Mg)TiO3-based multilayer ceramic capacitor (MLCC) sintered at 925 °C for 2 h to evaluate the effect of the inner electrode on reliability. The main results show that the lifetime is inversely proportional to Ag content in the Pd/Ag inner electrode. Ag+1 diffusion into the (Zn,Mg)TiO3-based MLCC during cofiring at 925 °C for 2 h and Ag+1 migration at 140 °C against 200 V are both responsible for the short lifetime of the (Zn,Mg)TiO3-based MLCC, particularly the latter factor. A (Zn,Mg)TiO3-based MLCC with high Ag content in the inner electrode Ag/Pd=99/01 exhibits the shortest lifetime (13 h), and the effect of Ag+1 migration is markedly enhanced when the activation energy of the (Zn,Mg)TiO3 dielectric is greatly lowered due to the excessive formation of oxygen vacancies and the semiconducting Zn2TiO4 phase when Ag+ substitutes for Zn+2 during co-firing.

Preparation and Characterizations of ZnTiO3 Powders by Sol?Gel Process

ZnTiO3 powders were prepared by a sol–gel method. The gelation conditions and the gelation mechanism were investigated. The crystallization behavior and characteristics of the ZnTiO3 were also investigated in detail. The experimental results show that homogenous and translucent gels can be prepared when the gelation conditions are appropriate and the gelation temperature remains constant. The gel structure can be described as a network of Ti and O, in which zinc ions are well distributed. The ZnTiO3 phase can be detected by XRD in the powders calcined above 700 °C. The formation of ZnTiO3 is a slow reaction process, which leads to the development of large ZnTiO3 particles, with dimensions after calcination at 900 °C for 2 h in the range of 30–50 μm.

Influence of mechanical activation on synthesis of zinc metatitanate

Investigations of a ZnO-TiO2 binary oxide mixture during mechanical treatment were mainly focused on obtaining orthotitanate Zn2TiO4 with a spinel structure. Due to the specific way of energy transfer during mechanical treatment using a high-energy ball mill, the system passes through low temperature ZnTiO3 metatitanate phase formation. Mechanical activation was performed on an equimolar ratio mixture of ZnO and TiO2. The anatase phase was previously submitted to heat treatment for achieving a starting mixture rich in a rutile phase. Milling conditions were preset for observing the formation of a low temperature ZnTiO3 phase with a perovskite structure. The powder microstructure was characterized using scanning electron microscopy. A nitrogen gas sorption analyzer with the BET method was used to determine the specific surface area and porosity, indicating changes of powder sample properties during mechanical activation. Also, X ray powder diffractometry was applied to obtain the phase composition. Powders were then pressed into pellets and their compressibility was observed through density changes. According to microstructures obtained by scanning electron microscopy analysis, the system underwent a primary and secondary agglomeration process. Specific surface area measurements supported that conclusion. Compressibility investigations established the difference between compressibility of the non-activated mixture and activated powders. X-ray diffraction analysis revealed that a perovskite structure forms simultaneously with a spinel phase during the process of mechanical activation.

Low-fired microwave dielectrics in ZnO-TiO2 ceramics doped with CuO and B2O3

The microwave dielectric properties and the microstructure of low-firing zinc titanate ceramics have been investigated. The microstructure of these ceramics have been studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and it was found that CuO addition has the important effect of stabilizing the Zn2TiO4 phase. When the sintering temperatures are in the range of 870–950 °C, dielectric constant values (e r ) saturate at 21–25, the Q×f value is 20 000 GHz (at 10 GHz). The temperature coefficient of resonant frequency (τ f ) was 10 ppm °C−1. Therefore, the 0.5 wt %-CuO and 1.0 wt %-B2O3 doped ZnO-TiO2 ceramics can be used in multi-layer microwave devices requiring low sintering temperature.