Effect of suspension plasma spraying process parameters on YSZ coating microstructure and permeability

Suspension plasma spraying (SPS) is a modification of plasma spray processes that uses small feedstock powders suspended in a liquid to rapidly produce fully sintered, thin ceramic coatings with good microstructural control and no need for post-deposition heat treatments. This technique has been proposed as a potential next generation manufacturing method to fabricate metal supported solid oxide fuel cells (SOFC). This study produced SPS YSZ layers and characterized the effect of torch power and particle velocity on coating physical properties that are relevant to SOFC electrolyte performance such as density and permeability. The highest density (> 95% dense), lowest permeability coatings were produced from conditions with large plasma gas flow rates and small nozzles; however, these conditions resulted in low deposition efficiency. Coatings produced from conditions with slightly lower plasma gas flow rates and small nozzles were also fairly dense (93% dense) and had fairly low permeabilities, but had 70% higher deposition efficiency compared to the densest coatings.