Stability of the low temperature polymorphs (y and αα) of Lu-doped Y2Si2O7

The present study analyses the formation kinetics as well as the thermodynamic stability of the αα and y polymorphs of Lu-doped Y2Si2O7. The analysis has been carried out by means of both in situ and ex situ diffraction experiments. 29Si MAS-NMR spectroscopy has also been used to complement the information obtained from the diffraction measurements. The results indicate that both αα and y   polymorphs display the same temperature stability field (975∘C⩽T<1075∘C) although crystallization kinetics of αα seems to be faster than that of y.