Phase Transitions and Properties of Quartz Crystals

Quartz (SiO₂) exhibits a hallmark displacive phase transition between its low-temperature α-polymorph and high-temperature β-polymorph at approximately 573 °C. This reversible transformation involves subtle tilts and distortions of corner-sharing SiO₄ tetrahedra, driven by soft phonon modes and anharmonic lattice vibrations. The α-phase, stable at ambient conditions, possesses trigonal symmetry and exhibits strong piezoelectric and optical anisotropy, underpinning its use in timekeeping, sensors and frequency control. Above the transition temperature, the β-phase adopts hexagonal symmetry, characterised by dynamic disorder of oxygen atoms and enhanced symmetry that affects its elastic and dielectric properties. Under elevated pressures, additional polymorphs emerge, offering pathways to metastable phases with novel electronic and mechanical responses. Contemporary research combines advanced diffraction, spectroscopic and computational methods to unravel the atomic-scale mechanisms of these transitions, optimise material performance and guide the design of quartz-based devices for high-temperature and high-pressure applications.

Research from Nature Portfolio

Recent studies have employed synchrotron X-ray diffraction under dynamic compression to reveal atomic rearrangements during the α–β transition, demonstrating the role of anharmonic lattice vibrations in stabilising the high-temperature polymorph. First-principles molecular dynamics combined with in situ diffraction has mapped pressure-induced transitions beyond β-quartz, identifying metastable high-pressure polymorphs exhibiting enhanced piezoelectric coefficients. Inelastic neutron scattering experiments have resolved phonon dispersion curves across the phase boundary, highlighting a soft mode at the Brillouin zone edge that acts as the primary order parameter driving the displacive transformation.

Phase Transitions and Properties of Quartz Crystals publication trend

The graph below shows the total number of articles in phase transitions and properties of quartz crystals across all publications each year (not limited to Nature Index journals).

Technical terms

α–β transition: The reversible, displacive transformation between low-temperature trigonal and high-temperature hexagonal quartz polymorphs.

Soft mode: A low-frequency phonon whose frequency approaches zero at the phase transition, driving structural change.

Anharmonic lattice vibrations: Non-linear atomic motions that stabilise high-temperature crystal structures.

Pseudocubic parameterisation: A modelling approach that maps tetrahedral units onto an approximate cubic framework for structural analysis.

Ferroelastic domain: A region of uniform strain orientation separated by domain walls in a ferroelastic material.

Piezoelectricity: The generation of electric charge in a material upon mechanical stress.

References

1. Modelling the structural variation of quartz and germanium dioxide with temperature by means of transformed crystallographic data. Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials (2021).