TEMPERATURE-VARIATION OF ELASTIC PROPERTIES OF ALPHA-QUARTZ UP TO THE ALPHA-BETA TRANSITION

The temperature variations of normal mode frequencies of a specimen of alpha-quartz single-crystal have been measured nearly up to the alpha-beta transition (T-0 = 573 degrees C), and all of the independent elastic constants were determined simultaneously by the rectangular parallelepiped resonance method. The results demonstrate that bulk moduli decrease largely toward T-0, while shear moduli show only a slight decrease. The trigonal constant C-14 decreases just below T-0, but seems to remain a finite value even at T-0. It is noted that the isotropic aggregate of alpha-quartz is a curious and scarce material in the sense that its bulk modulus is smaller than the shear modulus, and Poisson's ratio is very small or even negative at temperatures higher than 450 degrees C. In the measured temperature variations of mode frequencies, a characteristic feature was observed when two branches of A(g) modes came close, suggesting mode coupling. Except for this coupling between A(g) modes themselves, no definite evidence was observed which was indicative of coupling between modes of different symmetry. So it can be said the present sample is uniform in its property enough to suppress the coupling between modes of different symmetry.