Instituto de Óptica “Daza de Valdés”

Correlation between structure and mechanical properties in α-quartz single crystal by nanoindentation, AFM and confocal Raman microscopy

Óptica para el espacio e iones de alta energía (GOLDION)

Madrid / November 7, 2023

A group of European researchers has carried out a study that reveals the correlation between the internal structure and mechanical properties in the α-quartz single crystal. This work has recently been published in the journal Journal of Materials Research and Technology.

α-quartz is a material widely used in many technologies, from applications in geology and solid-state physics (the study of rigid or semi-rigid matter) to devices and sensors, such as piezoelectric material for microbalances or oscillators for clocks, computers, etc. These applications are very sensitive to local pressures and stresses.

However, there is a lack of information in the scientific literature on the effect of high local pressures on the structure of quartz and its correlation with its mechanical properties.
In order to address this knowledge gap, the researchers conducted nanoindentation experiments in which a tip, usually diamond or sapphire, is driven into the material to learn its strength, elasticity, and other mechanical properties.
This entire process was analyzed with confocal Raman microscopy, a technique capable of obtaining detailed information on the structural deformation and mechanical properties generated by high local pressures.
Nanoindentation traces obtained using AFM and Raman images where permanent deformation is observed as a function of the applied load. /Journal of Materials Research and Technology
The study revealed that nanoindentation produces a permanent plastic deformation in the α-quartz single crystal, leading to the appearance of a new, denser quartz phase, from which information was obtained about its structure and the stresses propagated along the crystal. .

Furthermore, a correlation was established between the nanoindentation results and the structural data obtained by Raman spectroscopy. The researchers showed that the mechanical properties obtained by nanoindentation were being slightly overestimated due to the lack of consideration of the absorption effect. Likewise, it was evidenced that the load applied to the α-quartz single crystal during the discharge process triggers a phase transformation associated with ferroelastic behavior, whose contribution increases with the applied load.

This study provides a deeper understanding of the mechanical properties and structural changes in α-quartz under high local pressures. The findings are relevant to advancement in materials science and could have implications for the design and development of more efficient and robust devices and sensors.

The researchers involved in this study belong to the Department of Electroceramics of the Institute of Ceramics and Glass of the CSIC, to the CSIC Institute of Optics and RNANO Laboratory of the School of Chemical Engineering at the National Technical University of Athens.

Quartz, piezoelectric material

Piezoelectricity is a phenomenon that occurs in certain crystals that, when subjected to mechanical stress, acquire an electrical polarization in their mass, appearing a potential difference and electric charges on their surface. Quartz crystals are known as Crystal Resonators, with the advantage of being able to generate stable oscillation frequencies.

This phenomenon also occurs in reverse: they deform when subjected to an electric field. The piezoelectric effect is normally reversible: when the crystals are no longer subjected to an external voltage or electric field, they recover their shape.

IO-CSIC Communication

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