Gadolinium oxide solubility in molten silicate: dissolution mechanism and stability of Ca2Gd8(SiO4)6O2 and Ca3Gd2(Si3O9)2 silicate phases - Archive ouverte HAL Access content directly
Journal Articles Journal of the European Ceramic Society Year : 2017

Gadolinium oxide solubility in molten silicate: dissolution mechanism and stability of Ca2Gd8(SiO4)6O2 and Ca3Gd2(Si3O9)2 silicate phases

Abstract

Improvement of the calcium-magnesium aluminosilicate (CMAS) infiltration mitigation concept in thermal barrier coatings (TBC) requires fundamental data on thermochemical reaction involving rare-earth oxide candidate as ZrO2 alloying element. This study investigates, through a model approach, Gd2O3 dissolution at 1200 °C in a synthetic model CAS melt (64.4SiO2–9.3Al2O3–26.4CaO mol. %) and the stability of the precipitated Gd-apatite Ca2Gd8(SiO4)6O2 and Ca3Gd2(Si3O9)2 cyclosilicate phases. The two Gd-rich silicates have been synthesized by solid-state reaction and then characterized by X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDS). The interactions of Gd2O3, Gd-apatite and Gd-cyclosilicate with CAS have been observed by scanning electron microscope (SEM) after various times of contact at 1200 ̊C, giving information about dissolution/precipitation processes. Dissolution kinetics has been evaluated by electron probe microanalysis (EPMA) measurements in the CAS melt. A discussion is finally provided concerning the thermodynamic stability of all phases of the system and confronted with kinetics considerations.
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Dates and versions

hal-01559200 , version 1 (10-07-2017)

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François Perrudin, Céline Rio, M.H. Vidal-Sétif, Carine Petitjean, Pierre-Jean Panteix, et al.. Gadolinium oxide solubility in molten silicate: dissolution mechanism and stability of Ca2Gd8(SiO4)6O2 and Ca3Gd2(Si3O9)2 silicate phases. Journal of the European Ceramic Society, 2017, 37 (7), p. 2657-2665. ⟨10.1016/j.jeurceramsoc.2017.02.022⟩. ⟨hal-01559200⟩
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