Fabrication and properties of high B value [Mn_1.56Co_0.96Ni_0.48O₄]_1−x[SrMnO₃]_x (0 ≤ x ≤ 0.5) spinel–perovskite composite NTC films

The [Mn_1.56Co_0.96Ni_0.48O₄]_1−x[SrMnO₃]_x ((MCN)_1−x(SM)_x, 0 ≤ x ≤ 0.5) ceramic thin composite films were grown on SiO₂/Si (100) substrates by the chemical solution deposition (CSD) method. The results of X-ray diffraction showed that the (MCN)_1−x(SM)_x (0 < x ≤ 0.5) films were a resemblance of the spinel–perovskite composite structure. The field emission scanning electron microscope analyses presented a considerable improvement in relative density with the increasing of the SM contents. In particular, the thermal constant of (MCN)_1−x(SM)_x ceramic film increased from 3289 to 5390 K with the increasing of the SM contents (x) from 0 to 0.5. This feature was attributed to the increase in the grain boundary resistance and the increase in Mn³⁺/Mn⁴⁺ pairs as the SM contents increased. From the spectroscopic ellipsometer spectroscopy results, it was found that the (MCN)_0.5(SM)_0.5 film had the biggest refractive index n value of 2.36 at 1.5 eV and a strong absorption peak at 4.0 eV. The sensitivity of MCN spinel ceramic film was enhanced by the compounding of SM. It was a significant disposition in the study of negative temperature coefficient thermistors.