X-Ray Topographic Investigation on Phase Transition in Quartz. I. Experimental Observations

Phase transition in quartz was investigated in some detail for single crystals by high temperature X-ray diffraction topography. Twin formation was directly observed in the both directions of the phase transition, low-to-high and high-to-low. Movement of the twin boundaries in twinned crystal or twin formation in “single” crystal occurs on heating at a few degrees below the transition temperature. Twin boundaries move and triangular or needle-like substructures on the boundaries appear on further heating the specimen, but reduction in size of each twinned region is not observed. Observation of the coexistence of α and β phases supports that the α-β phase transition is of first order.