A study based on MgAl_2O_4-LaCrO_3 composite ceramics for high temperature NTC thermistors

摘要

The effects of the sintering process on the microstructure and high temperature electrical properties of xMgAl(2)O(4)-(1-x)LaCrO3 (x=0.3, 0.4, 0.5) composite ceramics were investigated. X-ray diffraction (XRD) results show that all the composite ceramic samples are composed of the spinel oxide MgAl2O4 phase and orthogonal perovskite structure LaCrO3 phase, and no impurities appear. The grain size of the vacuum sintered ceramic is smaller, resulting in an increase in electrical resistance. X-ray photoelectron spectroscopy confirmed the presence of Cr3+ and Cr (4+) ions at the lattice sites. The EDS results show that the vacuum sintered ceramic has more Cr content due to the smaller oxygen partial pressure during vacuum sintering. The activation energy of the vacuum sintered sample is higher than the activation energy of the conventional sintered sample. All the composite ceramic samples have negative temperature coefficient characteristics and the resistivity increases with the increase of MgAl2O4 content.