The effect of high pressure on Bz03 : crystallisation, densification, and the crystallisation anomaly

PC 1967  001-044

The crystallisation and densification of Bz03 at high pressure have been investigated using a Bridgman anvil device. Crystallisation has been observed at pressures as low as 4 kb and at temperatures as low as 210°C. A marked effect of water in increasing the overall crystallisation rate, and the increase in this rate with increasing temperature, have been demonstrated. Increases in density as large as 17%, and a strong effect of temperature in increasing densification, have likewise been shown. These observations are qualitatively similar to those previously reported on SiOz and show crystallisation at temperatures below the glass transition and at rates several orders of magnitude faster than predicted by existing kinetic theories. Previous observations on crystallisation, densification, and structure are summarised and compared with the present results in an attempt to explain the anomalous crystallisation behaviour shown by B203 at high and low pressures