Relationship between Microstructure and Electrical Properties of ZnO-based Multilayer Varistor

Abstract

In this study, two types of ZnO-based multilayer varistor (MLV) with two different dielectric layers (12 and 24 µm), sintered from 900 to 1000 °C for 2 h were prepared to investigate the effects of microstructure such as the grain size and number of grain boundaries between two adjourn electrodes on electrical properties. The results show that the grain size linearly increases with sintering temperature, which results in an increase in the capacitance of ZnO-based MLVs. In contrast, the number of grain boundaries between two adjourn electrodes linearly decreases with sintering temperature associated with a decrease in breakdown voltage, leakage current and nonlinear coefficient of ZnO-based MLVs. The energy absorption capabilities determined from the peak current (PC) measurements of ZnO-based MLVs with sintering temperature are reported. The optimum peak currents of ZnO-based MLVs can be obtained by sintering at 950 °C.

Inner Electrodes for Multilayer Varistors

“…The α‐values of the MLV/Pt specimens are around two times that of the MLV/AgPd specimens. The newly formed PdBi 2 O 4 phase is a semiconducting phase; 3 its presence may lead to the decrease of the α‐value 13 …”

Low‐temperature sintering and electrical properties of BBSZ glass‐doped ZnO‐based multilayer varistors

“…As it is known, a ZnO‐based MLV is one of grain boundary capacitors that grain particle serves as a conducting matrix and grain boundary acts as an insulating layer. Therefore, breakdown voltage depends on the number of grain boundaries between two inner electrodes, which means it is inversely proportional to grain size . Thus, the breakdown voltage of MLVs can be controlled by altering the number and thickness of the ceramic layers in their structure.…”

“…And the peak current I p does not change much as sintering temperature lower than 925°C, however, it abruptly drops to 27 A when sintered at 950°C. Basically, the peak current associates with many factors, such as the energy dissipation of ZnO grains, densification of MLVs, uniformity of dopant distribution, and the number of grain boundaries between two adjacent electrodes . The existence of anomalously large grains also causes the decrease of peak current .…”

Microstructure–Property Relationships for Low‐Voltage Varistors

“…The I – V characteristics of the specimens were measured using a DC current method at currents ranging from 1 μA to 0.05 A. The nonlinear coefficient (α value) was determined by measuring the voltage at the applied currents of 1 and 10 mA 12 …”

“…The nonlinear coefficient (a value) was determined by measuring the voltage at the applied currents of 1 and 10 mA. 12 Results Figure 2 shows the XRD pattern of the multilayer specimens with the layer thickness of 8 mm. Apart from ZnO and AgPd phases, a spinel phase (Zn 7 Sb 2 O 12 ), a pyrochlore phase (Zn 2 Bi 3 Sb 3 O 14 ), a Bi 2 O 3 phase, and a PdBi 2 O 4 phase are also found in the sintered specimens.…”