Sintering behavior of doped ZnO powders for high field varistors
The sintering of ZnO varistor precursor powders, doped with Co, Mn and different concentrations of Bi and Al, is investigated and discussed in relation with sintering models. One purpose of the present study is to provide information valuable for the fabrication of high field varistors. As the fundamental parameter of these electronic components is the breakdown voltage per unit of thickness, which is determined by the number of grain boundaries per linear dimension, the grain size and the sintered density are crucial variables, and the sintering is a central step in the manufacturing of such varistors. Sintering experiments performed at constant heating rate in a loading dilatometer provide data on the densification and creep of the compacted powders. Another goal of the present study is to provide an experimental basis for the interpretation of the evolution of the ratio between densification rate and creep rate in terms of competition between densification and microstructure coarsening. This is accomplished by taking advantage of the variety of sintering behaviors that takes place in the system ZnO-Bi-Al: the comparison of these behaviors allows us to correlate the macroscopic sintering parameters to the evolution of the microstructure. It results that, while in non-doped powders densification and coarsening develop in a balanced way, resulting in the constancy of the ratio between densification rate and creep rate, the effect of the dopants on the sintering kinetics alters such a balance, leading this ratio to vary. 17 figs.
- Research Organization:
- Lawrence Berkeley Lab., CA (USA)
- Sponsoring Organization:
- DOE/ER
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 6455598
- Report Number(s):
- LBL-29736; ON: DE91005233
- Country of Publication:
- United States
- Language:
- English
Similar Records
Process for fabricating ZnO-based varistors
Aluminum doping studies on high field ZnO varistors
Related Subjects
360601* -- Other Materials-- Preparation & Manufacture
42 ENGINEERING
426000 -- Engineering-- Components
Electron Devices & Circuits-- (1990-)
ALKALINE EARTH METALS
ALUMINIUM
BISMUTH
CHALCOGENIDES
COBALT
CREEP
CRYSTAL DOPING
CRYSTAL STRUCTURE
ELECTRICAL EQUIPMENT
ELECTRON MICROSCOPY
ELEMENTS
EQUIPMENT
FABRICATION
MAGNESIUM
MECHANICAL PROPERTIES
METALS
MICROSCOPY
MICROSTRUCTURE
OXIDES
OXYGEN COMPOUNDS
RESISTORS
SCANNING ELECTRON MICROSCOPY
SEMICONDUCTOR DEVICES
SEMICONDUCTOR RESISTORS
SINTERING
TEMPERATURE DEPENDENCE
TRANSITION ELEMENTS
ZINC COMPOUNDS
ZINC OXIDES