NTC Thermistors of Y-Al-Mn-Fe-Ni-Cr-O Ceramics for Wide Temperature Range Measurement

NTC thermistors of Y-Al-Mn-Fe-Ni-Cr-O systems were fabricated by using normal ceramic processing for wide temperature range measurement. Pt-Rh alloy as electrodes was inserted into the body during the forming process to increase the reliability of high temperature and to decrease the contact resistance. The properties were analyzed by XRD, SEM and resistance measurement. There are no distinct XRD patterns between Y0.2Al0.1Mn0.27Fe0.16Ni0.27Ox and Y0.2Al0.1Mn0.264Fe0.16 Ni_0.264Cr_0.012O_x because of too small content of Cr₂O₃, as a dopant, to make peak difference or new phases within the XRD resolution. SEM images and resistance behaviors show the different properties. With the addition of Cr₂O₃ as a dopant, the crystallinity and the grain size were decreased and increased, respectively. The resistance behaviors were similar but the values are low with Cr₂O₃. The specimens show the straight line relationship between the electrical resistivity and the temperature over a wide temperature range, indicating NTC thermistor characteristics.