Zircon (ZrSiO4) is an inexpensive and widely available material with excellent thermal properties that makes it an ideal candidate for thermal barrier coatings. Previous works have demonstrated the feasibility of obtaining coatings with a high retention of zircon by plasma spraying of ZrSiO4 and ZrSiO4/ZrO2 suspensions. Suspensions of ZrSiO4/Al2O3 and ZrSiO4/TiO2 were produced by dispersing a micrometric zircon powder into alumina and titania colloidal sols, optimising their colloidal stability and rheological behaviour. Optimised slurries were plasma sprayed onto metallic substrates, obtaining coatings with the typical morphologies obtained by suspension plasma spraying (SPS). Nanostructured coatings with nanoparticles embedded in the molten matrix were obtained at higher proportions of sprayed colloidal sol. The high retention of ZrSiO4 in the final coatings and the formation of new crystallographic phases of mullite and zirconium titanate by reaction of the by-products of zircon decomposition (SiO2 and ZrO2) and the Al2O3 and TiO2 colloids was demonstrated. © 2024 The Authors

This research was funded by the Spanish Ministry of Science,Innovation and Universities (MCIU), the State Research Agency (AEI) and the European Regional Development Fund (FEDER) under project PID2021-124521OB-I00 and pre-doctoral fellowship PRE2019-091092. J. L.-S. acknowledges the financial support from Spanish Ministry of Economic Affairs and Digital Transformation (MINECO) through the project PID2021-122980OB-C51MCIN and from grant RYC2022-035912-I funded by MCIU/AEI/10.13039/501100011033 and by the European Social Fund Plus (ESF+) .r Innovation and Universities (MCIU) , the State Research Agency (AEI) and the European Regional Development Fund (FEDER) under project PID2021-124521OB-I00 and pre-doctoral fellowship PRE2019-091092. J. L.-S. acknowledges the financial support from Spanish Ministry of Economic Affairs and Digital Transformation (MINECO) through the project PID2021-122980OB-C51MCIN and from grant RYC2022-035912-I funded by MCIU/AEI/10.13039/501100011033 and by the European Social Fund Plus (ESF+) . +) .

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