Electrical properties and temperature sensitivity of Li/Fe-modified NiO-based ceramics as NTC thermistors

To develop a new system of negative temperature coefficient (NTC) thermistors, Li/Fe-modified NiO-based ceramics, Ni1-x-y Li (x) Fe (y) O (x: 0.00-0.08; y: 0.00-0.06), were prepared through a wet chemical process. The phase component and microstructure of the ceramics were analyzed respectively by using X-ray diffraction and electron microscopy, and the related electrical properties were investigated by resistance-temperature measurement and complex impedance analysis. The results show that all the ceramics have the cubic-type NiO crystalline structure and show typical NTC characteristic. The NTC material constant B (25/85) ranges from 335 to 5169 K and room-temperature resistivity ln rho (25) ranges from 3.97 Omega cm to 1.99 M Omega cm, when the ceramics were modified by various contents of Li- and Fe-ions. The conduction mechanisms combining the electron-hopping model and band conduction are supposed for the NTC effect in the Li/Fe-modified NiO ceramics.