A pressure-induced phase transformation in the lithium aluminum silicate b-eucryptite was studied with in situ Raman spectroscopy. Dense b-eucryptite composites were made via powder synthesis followed by sintering. The specimens were then subjected to diamond indentation up to applied contact stresses of about 8 GPa, while collecting Raman spectra. The appearance of a Raman peak (B520 cm À1 ) at a contact stress of about 3 GPa likely corresponds to the reversible phase transformation of b-eucryptite to the orthorhombic phase e-eucryptite. Loading and unloading in situ Raman indentation experiments are discussed with regards to this transformation.C. Landis-contributing editor
The reaction sequence to synthesize β‐eucryptite, LiAlSiO4, from the raw ingredients SiO2, Li2CO3, and Al2O3 was studied using thermal analysis and X‐ray diffraction techniques. Reactions were examined by heating the raw ingredients as two‐component and three‐component mixtures in air, then cooling for phase analysis. In some cases, cyclic heating was performed to ensure a complete reaction. It was found that a complex sequence of reactions involving several intermediate phases occurs. The single oxides (SiO2 and Al2O3) react with Li2CO3 to form the binary oxides (Li2Si2O5, Li2SiO3, and LiAlO2); SiO2 reacts with Li2CO3 before Al2O3. Subsequently, the binary oxides form ternary oxides (LiAlSi2O6 and LiAlSiO4). Finally, the ternary oxides form the equilibrium product, β‐eucryptite (LiAlSiO4). These reactions are discussed in the context of the thermodynamic properties of the various compounds.
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