Study of quartz sweeping in α and β phases

Synthetic samples in the α phase at 550°C and in the β phase at 650°C were studied with air and vacuum atmosphere and Pt foil electrodes. The electrical current variation was measured both during sweeping and final cooling, giving activation energies in the α and β phase. The samples were characterized by IR measurements at 77 K: a complete disappearance of the OH lines was observed after vacuum sweeping in the α phase (550°C-3500 V/cm) or in the β phase (650°C-1500 V/cm). Considerable modification of the birefringence variations within the incommensurate phase was found. Samples that are heated in the β phase become twinned; however, a torque can detwin the major part of a AT-cut twinned sample