LaMn1-xTixO3-NiMn2O4(0 ≤ x ≤ 0.7): A composite NTC ceramic with controllable electrical property and high stability

A series of NTC thermistor ceramics based on LaMn1-xTixO3-NiMn2O4(0 <= x <= 0.7) composite system have been fabricated by solid-state method. X-ray diffraction analysis indicates the composite ceramics mainly consisting of a rhombohedral perovskite LaMn1-xTixO3 phase and a cubic spinel NiMn2O4 phase. SEM images show high density of the as-prepared composite ceramics. The effects of the Ti doping and the weight ratio of LaMn1-xTixO3/NiMn2O4 on electrical property have been studied. The electrical resistivity rho increases significantly with Ti addition increasing and decreases obviously with LaMn1-xTixO3 concentration increasing. The rho(25 degrees C) and B values are in the range of 3.2-53,200.0 Omega.cm and 1300-4008 K, respectively, and could be adjusted to desired values and applied in various fields. The conductive mechanism may be related to the ion migration and the percolation theory. After annealing at 125 degrees C for 1000h, the resistance shifts are less than 0.52%, suggesting good stability of the composite and high potential for NTC thermistor applications.