Microstructure and Electrical Properties of Fe,Cu Substituted (Co,Mn)3O4 Thin Films

Abstract

Abstract:In this work, thin films (~1000 nm) of a pure MnCo 2 O 4 spinel together with its partially substituted derivatives (MnCo 1.6 Cu 0.2 Fe 0.2 O 4 , MnCo 1.6 Cu 0.4 O 4 , MnCo 1.6 Fe 0.4 O 4 ) were prepared by spray pyrolysis and were evaluated for electrical conductivity. Doping by Cu increases the electrical conductivity, whereas doping by Fe decreases the conductivity. For Cu containing samples, rapid grain growth occurs and these samples develop cracks due to a potentially too high thermal expansion coefficient mismatch to the support. Samples doped with both Cu and Fe show high electrical conductivity, normal grain growth and no cracks. By co-doping the Mn, Co spinel with both Cu and Fe, its properties can be tailored to reach a desired thermal expansion coefficient/electrical conductivity value.

Deposition and Electrical and Structural Properties of La0.6Sr0.4CoO3 Thin Films for Application in High-Temperature Electrochemical Cells

“…A very high stress calculated in this work for the LSC layers does not result in visible cracking or delamination of the thin films. Previously, for a similarly deposited MnCo 1.6 Cu 0.4 O 4 layer on sapphire we have observed cracking due to increased TEC after Cu doping, 54 but the absolute value was still much lower than for the LSC, which is typically regarded as a material with a high TEC (at least among the SOFC materials). One possible explanation for lack of cracking might be that due to interdiffusion between the sapphire and the LSC layer a very strong interface is formed and the properties of the thin layer are modified due to interdiffusion.…”

Comparison of iron and copper doped manganese cobalt spinel oxides as protective coatings for solid oxide fuel cell interconnects

“…Both materials have appreciable electrical conductivity (60-90 S cm -1 at 800 °C [11,12]) and an acceptable thermal expansion coefficient (TEC) (11.4-14.4×10 -6 K -1 between 25 °C and 800 °C [13][14][15]). Attempts to improve the (Mn,Co) 3 O 4 coating material by substituting some of the Co with Fe or Cu have been reported [13,[16][17][18][19][20][21]. The TEC of MnCo 2 O 4 is reduced by replacing some of the Co with Fe, which in some cases may be advantageous depending on what type of cell the interconnect is connected to [15].…”

Evaluation of electrodeposited Mn‐Co protective coatings on Crofer 22 APU steel

“…They differ more visibly at the high temperature range, between 0.73 eV and 0.88 eV (~20% variation). Several authors have reported a change in the slope of the conductivity of the spinel materials, also when used on the alloys . Activation energy of the oxidized alloys is depending on the properties of not only the coatings, but also on the properties of the thermally grown chromia layer and other possible reaction layers, which due to its low electronic conductivity and high activation energies dominates the scale resistance.…”

“…Oxidation behavior of alloys coated with different Mn/Co coatings remains to be reported. Additionally, spinel might be doped with either Fe or Cu to tailor its properties, enhance sintering and match the thermal expansion coefficient to other stack components …”