Effect of substrate surface temperature on the microstructure and ionic conductivity of lanthanum silicate coatings deposited by plasma spraying
W.Z. Wang, F. Sun, X.P. Guo, H.L. Liao, O. Elkedim, J.C. Liang
Surface & Coatings Technology
abstract
Apatite-typ e lanthanum silicate shows a high ionic conductivity and low activation energy at intermediate temperature (600– 800 °C) compared with Yttria stabilized Zirconia (YSZ). In addition, its excellent stability in a wide oxygen partial pressure range meets the requirement for the electrolyte. Thus it is a potential candidate for intermediate temperature solid oxide fuel cell (IT-SOFC) electrolytes. Moreover, atmosph eric plasma spray ing is expected to be a promising alternative to other costly or low-depo sition rate electrolyte processing methods. However, the amorphous phase and pores existing in the plasma sprayed coatings might impair the stability and the higher ionic conductivity of lanthanum silicate . The present work investigated the effect of substrate surface temperature from 545 °C to 900 °C on the microstructure and ionic conductivity of the lanthanum silicate coating. The crystallinity of as-deposited coatings increased with the incre ase of substrate surface temperature, whereas the porosity sho wed a con trary tendency. Ionic conductivity increased about four times with incre asing substrate surface temperature, which is related to the low porosity and high crystallinity of coatings. Increasing the substrate surface temperature durin g plas ma spraying is a feasible method to incre ase ionic conductivity of the lanthanum silicate coatings by reduc ing the porosity and enhancing the crystallinity.
keywords: Atmospheric plasma spraying,Lanthanum silicate,Ionic conductivity,Substrate temperatu re analysis
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