In Situ Raman Indentation of β‐Eucryptite: Characterization of the Pressure‐Induced Phase Transformation

Abstract

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

Determining Activation Volume for the Pressure‐Induced Phase Transformation in β‐Eucryptite Through Nanoindentation

“…The behavior was attributed to two different mechanisms: (1) the energetic release of residual stresses arising due to the large CTE anisotropy and (2) a reversible phase transformation involving a 7.7% volume change. Subsequently, Jochum et al . carried out in situ Raman indentation studies which proved the existence of a reversible phase transformation during indentation.…”

“…calculated the lattice volume of orthorhombic ε‐eucryptite to be 7.7% lower than that of β‐eucryptite. Furthermore, this transformation is seen to be reversible, i.e., ε‐eucryptite reverts back to β‐eucryptite on the release of pressure at ambient temperature . However, pressures greater than 0.83 GPa at higher temperatures (~600°C) result in an irreversible transformation to α‐eucryptite.…”

“…Macro‐indentation studies have yielded valuable information about the phase transformation in β‐eucryptite . In 2007, Reimanis et al .…”

A tension stress loading unit designed for characterizing indentation response of single crystal silicon under tension stress

“…[1][2][3][4][5] Kinds of testing methods have been developed to characterize mechanical properties of single crystal silicon in mm ∼ nm scales, such as micro/nano-indentation testing, 6-8 scratch testing, 9,10 cyclic loading testing, 11,12 microcompression testing, 13 microbending testing 14 as well as combined in situ testing and analysis methods. 15,16 Among these testing methods, micro/nano-indentation testing plays a very important role for characterizing mechanical properties of single crystal silicon because of its high testing resolution and nearly non-destructive testing. Some interesting phenomena corresponding to phase transformations of single crystal silicon beneath the indenter, such as pop-out and elbow, have been observed by indentation testing.…”

Reactions in Eucryptite‐Based Lithium Aluminum Silicates

“…The transformation has been observed by in situ synchrotron X-ray diffraction (XRD) as well as in situ Raman spectroscopy. 6,7 This unique behavior motivates fundamental studies to understand better the material structure-property relationships.…”