Songklanakarin Journal of Science and Technology (SJST) (Sep 2005)
The new types of positive temperature coefficient effect based on SnO2+2CoO and SnO2+Cr2O3 ceramics used as temperature sensor
Abstract
The SnO2+2CoO and SnO2+Cr2O3 materials were prepared by standard ceramic techniques and the phase identified by XRD techniques. The PTC effect was tested. Both samples were applied as temperature sensors. Sample 1 exhibited PTC effect from 25 to 110ºC and the positive temperature coefficient of the resistance (α) was +18.2 %/ºC. The maximum resistance was 28.5 MΩ at 110ºC. Sample 2 exhibited PTC effect from 35 to 85ºC and the positive temperature coefficient of the resistance (α) was +28.6 %/ºC. The maximum resistance was 91.8 MΩ at 85ºC. The PTC effect was seen to have its origins in the resistance of the grain boundary region. The PTC effect in both samples was discovered for the first time. The prepared samples and temperature monitoring with a computer system can measure the temperature in the range 22ºC to 70ºC (sample 1) and 40ºC to 120ºC (sample 2). The working temperature of these sensors are near the PTC region and they are very sensitive to heat.
