The transition from non-ohmic to ohmic characteristics in La2O3 doped ZnO–MgO–TiO2 linear resistance ceramics

Abstract

La2O3 doped ZnO–MgO–TiO2 based linear resistance ceramics were prepared by the solid phase sintering method. The doping content of La2O3 is from 0.0 wt% to 2.5 wt%. The solubility of La2O3 in ZnO is less than 0.06 mol% (0.5 wt%), La0.66TiO2.993 phases will be formed at grain boundary and change the distribution of spinel phase when La2O3 is excessive. For I–V test, undoped sample exhibits typical non-ohmic characteristics, but La-doped samples show excellent ohmic behaviors under low DC and high pulse current (PC). The complex impedance spectrum and the frequency dependent conductivity furtherly demonstrate that La-doped samples possess linear characteristics because there is no grain boundary effect which can affect the electron transmission at grain boundaries. Besides, the decrease of the grain boundary barrier from 0.2135eV for undoped sample to 0.0031eV for 0.5 wt% La doped samples can account for the elimination or reduction of grain boundary effect. In this work, the transition from non-ohmic to ohmic properties by doping La2O3 in ZnO–MgO–TiO2 multiphase ceramics is realized.