X-RAY LANG TOPOGRAPHY AND INFRARED-SPECTROSCOPY IN QUARTZ CRYSTALS GROWN HYDROTHERMALLY WITH INTERMITTENT RUNS

Growth defects in Y-plates obtained from Y-bar synthetic quartz crysta ls, grown hydrothermally with intermittent runs, have been studied for the first time by X-rag Lang topography and infrared spectroscopy. To study the effect of interfaces on dislocation structures, the growth I uns have been discontinued several (6 to 7) times by switching off t he autoclaves from 30 min to 1 h. The dislocations were observed to ch ange their directions at the generated interfaces, sometimes they stop at the interfaces or move straight through the interfaces depending o n the angles of the interfaces which are presumably low-angle grain bo undaries. The percentage transmission of infrared beam has also been m easured as a function of the distance traversed in the crystal. ?he in verse anelastic loss (Q) decreases at the interface which is due to th e greater accumulation of chemical impurities and H bonded OH- ions at these interfaces. The effect of in-situ electric field on the topogra phic contrast has also been studied which reveal some interesting resu lts on account of space charge polarization.