Effect of Solution Chemistry on Solution Precursor Plasma Spray Deposition

Solution precursor plasma spray (SPPS) could deposit coatings consist of grains or particles as small as ~20nm , and may be relatively porous or nearly dense, depending on deposition parameters.  Recently, the SPPS demonstrates the potential to deposit fine particle size and porous coatings suitable for use as electrochemical electrodes for fuel cells and gas sensors. Most of the times, crystal structure plays the most important roles in determining the performance of the electrodes among porosities and surface areas. For example, LiFePO4 crystal structures phase instead of Li3Fe2(PO4)3 phase.

This paper investigates the effect of solution chemistries on crystal structures deposited by SPPS for electrochemical electrodes. Solutions containing lithium, iron and phosphorus ions are injected into a hydrocarbon plasma issuing from a DC-arc torch. The pyrolysis of each solution is investigated by XRD and DTA/TGA at stepwise decomposition temperatures. The chemistry of plasma jet with each solution precursor is investigated by spectrometers. The resulting coating morphologies and phase composition were studied. The results indicate that the porosity and crystal structure of the coatings can be tailored by selecting different solutes, additives and solvents.