Reaction Products from High Temperature Treatments of (LaxGd1x)2Zr2O7 System and Volcanic Ash Powder Mixtures

• Main Authors: Guijosa-Garcia, Cynthia Y., Rivera-Gil, Marco A., Ramana, C.V., Naraparaju, Ravisankar, Schulz, Uwe, Muñoz-Saldaña, Juan
• Format: Other Non-Article Part of Journal/Newspaper
• Language: English
• Published: Springer Nature 2022
• Subjects: Hochtemperatur-und Funktionsschutzschichten; Eyjafjallajökull
• Online Access: https://elib.dlr.de/187543/; https://elib.dlr.de/187543/1/Guijosa23Eli-DLR.pdf; https://www.springer.com/journal/11837/?gclid=Cj0KCQjwidSWBhDdARIsAIoTVb2eKdqlSs_6vadsBfkJS8P2HviJyh4blEL62bQ_7b9ni5R6iIEdNCQaAr91EALw_wcB

Rare-earth zirconate (REZ) pyrochlores, specifically (La,Gd)2Zr2O7, are promising alternatives to substitute 7YSZ in thermal barrier coatings (TBC) due to their increased phase stability and resistance to calcium-magnesium-aluminosilicate (CMAS)-based damage at high temperatures. This work analyses the reaction products of isothermal treatments at 1250°C of (LaxGd1−x)2Zr2O7 powder mixtures in reaction with natural volcanic ashes (VAs) with different chemical compositions (Popocatepetl, Colima, and Eyjafjallajökull). The chemical composition in the (LaxGd1−x)2Zr2O7 system showed a strong influence on the formation of reprecipitation products (Zr,Gd,La oxides), reactive crystallization products (La-Gd apatites, lanthanum silicates, zirconolite, and garnets), and intrinsic crystallization products (hematite-like structures). The formation of garnets, which enhances the mitigation effect against molten VAs/Si deposit damage, was observed more promptly on (La0.5Gd0.5)2Zr2O7 promoted by high contents of Fe, Ca, Ti, and Mg on VAs. Thus, the (La0.5Gd0.5)2Zr2O7 system stands as a possible candidate to overcome today’s threats for the integrity of current TBCs.