Characterization of temperature induced resistivity jump in Li/Y/Cr co-doped ZnO ceramics

ZnO-based ceramics, (Zn0.9725Y0.0025Cr0.025)1−xLi x O (x = 0, 0.02, 0.05, 0.07, and 0.10), were prepared by a wet chemical route followed by a traditional ceramic sintering technology. The phase component, electrical properties, and resistivity-temperature characteristic of the prepared ceramics were investigated. The results reveal that all the prepared ceramics have a wurtzite type crystalline structure, and show an abnormal resistivity-temperature characteristic as that of the typical positive temperature coefficient (PTC) thermistors. The ZnO-based ceramics exhibit high resistivity jump with the log(ρmax/ρmin) higher than 3.13, and have a high resistivity temperature coefficient (α) of about 43–65% K−1, accompanying with the Curie temperatures changing from 313 to 386 K for various Li contents. The analysis of impedance spectra reveal that both grain effect and grain boundary effect contribute to the conduction and PTC effect of the studied ceramics.