Abstract
The ZnO doped with Al2O3 showed the minimum electrical resistivity at an Al2O3 content of 0.25%. It was found that the ZnO doped with
Al2O3 exhibited the resistance-temperature characteristic reversion from negative temperature coefficient of electrical resistivity (NTCR) to
positive temperature coefficient of electrical resistivity (PTCR) at temperatures of about 450 and 250°C for ceramics sintered at 1400 and 1300°C,
respectively. Both NTCR and PTCR features were weakened for samples with lower Al2O3 content or sintered at a higher temperature.
Microstructure studies exposed that the densification process was significantly depressed when the Al2O3 addition levels were over about 1%.
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