Structural and Electrical Properties of Nickel Manganite Ceramics for NTC Thermistor Material

Abstract

NixMn3-xO4 (0.71 = x = 1) systems were prepared using the mixed-oxide method. X-ray diffraction patterns confirmed the spinel cubic polycrystalline structure. All compositions showed a uniform and void-free grain structure with an average grain size of 5.27 mu m. In the IR adsorption spectra, the high frequency band (nu(1)) and low frequency band (nu(2)) are attributed to the tetragonal and octahedral complexes, respectively. The adsorption band nu(2) decreases slightly with the increasing content of nickel ions while band nu(1) remains constant in the range of x <= 0.79 and decreases with an increase in the content for x >= 0.88. In the range of x <= 0.79, Ni2+ ions mainly occupy B-site, however, for x > 0.79 the number of Ni2+ ions at in A-sites increases with increasing x, while the amount of Ni2+ ions in B-sites remains unchanged. Electrical resistivity and activation energy were significantly influenced by the cation distribution, i.e., the Mn3+/Mn4+ ratio in the octahedral sites. These values for the Ni0.79Mn2.21O4 specimen were 2602 Omega-cm and 0.321 eV, respectively.