Electrical conductivity and temperature sensitivity of W/F-modified CuO-based ceramics

>In order to develop new system of thermal sensitive ceramics with negative temperature coefficient (NTC) of resistivity, W/F modified CuO-based ceramics (Cu_1-yW_yO:F_x, xranges 0.01~0.07 and yranges 0~0.006)were prepared by using a wet-chemical synthesis method. The phase component, microstructure, electrical conductivity and resistivity-temperature characteristics of the ceramics were analyzed by using X-Ray diffraction, scanning electron microscope, resistance-temperature measurement and electrochemical impedance spectrum, respectively. The results show that the room temperature resistivities of the CuO ceramics can be adjusted obviously by doping with F ions, and the W/F-doped CuO ceramics have excellent NTC feature with the highest materials constant of 5084 K. The electrical conductivity and NTC characteristics of the W/F modified CuO ceramics are co-resulted from the grain effect (bulk effect) and grain-boundary effect. Both the band conduction and electron-hopping models are proposed for the conduction mechanisms in the W/F modified CuO ceramics.