A novel type of incommensurate phase in quartz: The elongated-triangle phase.

We present evidence for a thermodynamically stable incommensurate elongated-triangle (ELT) phase in quartz, observed by transmission electron microscopy at the α–β structural transition. The phase sequence on cooling is: incommensurate equilateral-triangle (EQT) phase (ferroelectric)—incommensurate ELT (ferroelectric and ferroelastic)—uniform α phase. The ELT blocks could be responsible for the large light scattering in the vicinity of the α–β transition. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]