HYDROTHERMAL GROWTH OF QUARTZ FROM AMMONI UM FLUORIDE SOLUTION

The solubility of quartz from ammonium fluoride solution was measured using a small autoclave. Based on the solubility data, a single crysta l of quartz was grown from ammonium fluoride solutions at 230-280-degr ees-C and 4-101 MPa. The growth rate depended on the growth temperatur e, temperature gradient and concentration of the ammonium fluoride sol ution. The maximum growth rate of the Z face attained was 0.88 mm/day which was comparable to that in alkaline solutions. However, the growt h rate of the X face was very low, the growth rate of - X face was les s than one fifth of that for + X face. Fine pyramidal growth hills wer e observed on Z face, and the size increased with increasing pressure and concentration of ammonium fluoride solution. The linear defect den sity in Z growth zone was about 10(3)-10(5) pcs/cm2, higher than that in alkaline solutions. Strong absorption at about 3500 cm-1 by - OH st retching vibration was observed in FTIR spectra. The defects originati ng from -OH depended on the temperature gradient.