Novel Cr-Mn-Fe-Co-Ni oxide composites fabricated by in situ spark plasma sintering for high-temperature applications

Spinel composite is being considered for electrode materials in molten salt electrolysis, aiming to improve high temperature stability and conductivity. Multi-phase composites with the general formula of (Fe1-3x-y Niy Cox Crx Mnx)3 O4 (x = 0.03, 0.06, 0.09, y = [1-2x]/3) were prepared via in situ SPS method. The composites were confirmed to consist of spinel and rock-salt phases through XRD and SEM analysis. Compared to the Ni-Fe-O system, the doping of Cr, Mn and Co improved the phase stability of the spinel during SPS, but hindered the shrinkage process. These composite exhibited low thermal diffusivity (1.236-2.481 m2/s, room temperature) and low coefficient of thermal expansion (9.8 14.4 x 10-6 K-1, 400-800 degrees C). Moreover, the composite with x = 0.06 and y = 0.29 exhibit 94.4 % lower permittivity, 7 times higher dielectric loss (at 40 Hz) and 26.6 % lower high-temperature conductivity (at 800 degrees C) than that of Ni-Fe-O system. This work demonstrates the enhanced thermal and electrical properties of spinel-based composites, which can provide inspiration to researchers and promote the development of high-temperature electrodes.