Low-temperature Synthesis and Negative Temperature Coefficient Conductivity Properties of Mn–Ni–Cu–O Spinel Ceramics

In response to the problems of high energy consumption and high-temperature instability in the preparation of ceramics and the need for low-temperature co-fired processes, some methods of reducing the sintering temperature of ceramics are needed for promising applications. The low-temperature solid-state method is a simple method to prepare materials, and it synthesizes precursors with small particle size and uniform element distribution, which has wide applicability in large-scale materials preparation. To compare the performance differences between Mn–Ni–Cu–O precursors and ceramics prepared using the low-temperature solid-state (LTSS) method and the high-temperature solid-state (HTSS) method under the same sintering condition. The temperature at which the two precursors form a pure spinel phase is revealed by X-ray diffraction analysis. The LTSS precursor forms a pure phase at 650 °C, which is 250 °C lower than that of the HTSS precursor, and the reasons for decreasing the pre-annealing temperature by the LTSS method are discussed. A comparison of the electrical properties of the two ceramics reveals that LTSS ceramics sintered at 1050 °C, which is 100 °C lower than that of the HTSS method, can obtain 96.9% relative density, high sensitivity (− 3.19%K−1), and low activation energy (0.236 eV). The conductivity mechanism is explored by XPS and complex impedance spectroscopy.