Abstract
In this work, thin films (~1000 nm) of a pure MnCo2O4 spinel together with its partially substituted derivatives (MnCo1.6Cu0.2Fe0.2O4, MnCo1.6Cu0.4O4, MnCo1.6Fe0.4O4) 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.
Highlights
The chemical compositions of the coatings have been evaluated by the energy dispersive spectroscopy (EDS) analysis at a low magnification (500×) to average over a large area
MnCo1.6Cu0.2Fe0.2O4 have been prepared by spray pyrolysis at 390 °C
Maximum electronic conductivity is found for layers experiencing a maximum produce dense spinel layers at temperatures of only 800 ◦ C, which is lower than for standard ceramic processing temperature of 700 °C, whereas no changes in the activation energy were noticed for processing methods
Summary
Materials based on MnCo2 O4 are interesting for a broad range of applications, from room temperature to high temperatures (800 ◦ C). They can be used in Li-ion battery electrodes [6,7], electrochemical supercapacitors [8] and as coating materials for steel interconnects for fuel cells [9,10,11]. The microstructure and the composition of the spinel strongly affect its performance and applicability in a specific technology. In recent years, doping of the spinel by either Fe or Cu has been pursued in order to increase its electrical conductivity, enhance sintering and possibly alter the thermal expansion coefficient [12,13]. Very recently has simultaneous substitution by both Fe and
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