Advances in the synthesis of ZnO nanomaterials for varistor devices

Abstract

adZnO based varistors are widely used for overvoltage protection in many electrical and electronic circuits, at voltages ranging from a few to over a million volts. By careful control of the microstructure, through nanostructuring by chemical routes, it should be possible to produce varistors with high breakdown voltage (V c ), as this is proportional to the number of active grain boundaries in the sintered body. This property is particularly important for the production of the small-sized varistors needed for modern electronic instruments such as tablet computers and mobile phones. The current review will outline the recent advances in the chemical processing (e.g. sol-gel, combustion synthesis plasma pyrolysis, micro-emulsion synthesis and precipitation routes) of varistors from ZnO nanomaterials and the properties of these materials. Uncontrolled grain growth at higher temperature is highlighted as a major challenge for obtaining desirable electrical properties for nano-varistors. Various novel sintering techniques such as step-sintering, spark plasma and microwave sintering methods are expected to deliver a varistor with controlled grain growth and optimum electrical characteristics.

Antibacterial properties of F-doped ZnO visible light photocatalyst

“…Zinc oxide (ZnO), a wide band gap semiconductor (3.37 eV), has a vast range of applications which include but are not limited to photocatalysts [8], varistors [9,10], pharmaceutical products [11], and lasers [12]. As a photocatalyst, in the presence of UV radiation, ZnO facilitates production of reactive oxygen species (ROS) on its surface [13].…”

Synthesis of monodisperse ZnO nanostructures via a solvent extraction route and its use in varistor ceramics

“…The breakdown voltage was measured at 1.0 mA/ cm 2 . The nonlinear exponent (a) is defined by a = (logJ 2 -logJ 1 )/(logE 2 -logE 1 ) [15], where E 1 and E 2 are the breakdown voltages responding to J 1 = 0.1A/ cm 2 and J 2 = 1A/cm 2 .…”

Study on the Frequency and Temperature Dependent Electrical Properties of MnO and PbO Doped ZnO Nanoceramics

“…Therefore, numerous studies are suggesting the grain boundary phenomena Of ZnO-Bi 2 O 3 and ZnO-V 2 O 5 based ceramic systems studied the influence of MnO 2 , PbO and a mixture of MnO 2 , PbO and B 2 O 3 on electrical and dielectric properties of ZnO-V 2 O 5 ceramics by alternating current (AC) impedance and variable temperature dielectric spectroscopy and found that the Schottky barrier present at grain boundary is much more important for varistor performance [10][11][12]. The electrical conductivity of Mn doped and Co doped ZnOBi 2 O 3 varistors were investigated using complex plane modulus analysis and found that the ratio of grain boundary to grain resistance of Mn doped samples is higher than that of Co doped samples [13].…”