X-Ray Studies of Crystals Vibrating Piezoelectrically

The original investigation has been extended by using both Laue patterns and regular reflection from the crystal surfaces. Much of the previous work was repeated and confirmed. Quartz was found to be more satisfactory for this work than Rochelle salt. A large increase of intensity in the Laue pattern was found for the fundamental of the low frequency mode of vibration with a $Y$-cut quartz crystal. The large increases found in previous work were due to the high frequency or "thickness" modes of vibration. The modes of vibration determined by the longer dimensions of the crystals gave an intensity increase for the case of regular reflection. It was shown that the negligible increase for the modes of vibration determined by the thickness of the crystals was not caused by an imperfect surface layer. In a complete survey made of a long $X$-cut crystal, a definite distinction was found between the regions of nodes and antinodes of motion. By direct polishing experiments, it was found that the intensity increases for the cases of regular reflection were due mainly to a reduction of secondary extinction. It is pointed out that in all cases these x-ray methods show a difference in the effect between the $X$-cut and $Y$-cut crystals for similar modes of vibration.