Critical positive temperature coefficient of resistivity of Li/Y co-doped ZnO ceramics modified by Cr-ions

摘要

ZnO-based ceramics doped with Li/Y and modified by various contents of Cr-ions, (Zn_(0.9475)Y_(0.0025)Li_(0.05))_(1-x)Cr_xO (0 ≤ x ≤ 0.025), were prepared by a wet chemical route followed by a traditional ceramic sintering technology. The effect of Cr-ion content on the electronic conductivity and resistance-temperature characteristics of the prepared ceramics was investigated. All the ceramics have hexagonal wurtzite ZnO structure, and exhibit critical positive temperature coefficient of resistivity (C-PTCR) effect. With various contents of Cr-ions, the maximum temperature coefficient of resistivity (TCR) reaches 61.1%°C~(-1) or the resistivity jump log(p_(max)/p_(min)) is up to 4.74. The critical transition temperature of resistivity can be adjusted in the temperature range of 76-147 °C for different various contents of Cr-ions. The complex impedance analysis shows that the C-PTCR effect of the ZnO ceramics resulted from both grain effect and grain boundary effect. According to the analysis of the dielectric temperature spectra, the ZnO-based ceramics have ferroelectricity at room temperature, and the ferroelectric-paraelectric transition around the critical transition temperature of resistivity during the temperature increases.