Hongming Yuan

Microstructure and electrical properties of Lu2O3-doped ZnO-Bi2O3-based varistor ceramics

Lu2O3-doped ZnO-Bi2O3-based varistor ceramics samples were prepared by a conventional mixed oxide route and sintered at temperatures in the range of 900-1 000 °C, and the microstructures of the varistor ceramics samples were characterized by X-ray diffractometry (XRD) and scanning electron microscopy (SEM); at the same time, the electrical properties and V-I characteristics of the varistor ceramics samples were investigated by a DC parameter instrument for varistors. The results show that the ZnO-Bi2O3-based varistor ceramics with 0.3% Lu2O3 (molar fraction) sintered at 950 °C exhibit comparatively ideal comprehensive electrical properties. The XRD analysis of the samples shows the presence of ZnO, Bi-rich, spinel Zn7Sb2O12 and Lu2O3-based phases.

Effects of high-energy ball milling oxide-doped and varistor ceramic powder on ZnO varistor

ZnO varistor ceramics doped with Bi2O3, Sb2O3, Co2O3, Cr2O3, and MnO2 were prepared separately by two high-energy ball milling processes: oxide-doped and varistor ceramic powder. A comparison in the electrical and microstructural properties of the samples obtained by both methods was made. The best results on these characteristics were achieved through the high-energy ball milling varistor ceramic powder route, obtaining a nonlinear coefficient of 57 and a breakdown field of 617 V/mm at a sintering temperature of 1000 °C for 3 h. The samples synthesized by this technique show not only high density value, 95% of the theoretical density, but also a homogeneous microstructure, which compete with those obtained by the high-energy ball milling oxide-doped powder route. With the advantage that the high-energy ball milling varistor ceramic powder route can refine grain, increase the driving force of sintering, accelerate the sintering process, and reduce the sintering temperature.

Effect of Al2O3 doping on electric and dielectric properties of ZnO linear resistor

Abstract Al doped ZnO linear resistors were prepared by the high energy ball milling. The effects of content of Al2O3 on the electrical properties of the linear resistors were investigated. Al doped ZnO reduces the non-linear coefficient to some extent at the sintering temperature of 1350°C. When the content of Al2O3 was 3·5 mol-%, the best performance of linear resistor of the non-linear coefficient 1·0 was obtained. The dielectric constant of ZnO linear resistors was the most stable over the frequency range of 1 00 000–10 000 000 Hz when the content of Al2O3 was 4·5 mol-%.