FERROBIELASTIC HYSTERESIS IN ALPHA-QUARTZ

The ferrobielastic behavior of α-quartz crystals under compressive stress has been investigated making use of the piezoelectric and piezo-optic effects. The direction of mechanical stress was so chosen that secondary twinning is favored. Above a threshold of approximately 0.5 GPa, ferrobielastic switching results in a complete orientation reversal. Unexpectedly the mere removal of the mechanical constraint leads to a complete restoration of the original orientation. This retrotransition occurs between 0.1 and 0.025 GPa. This effect is discussed in terms of a simple thermodynamical model.