Molar volumes and thermal expansions of andalusite, kyanite, and sillimanite

Thermal expansion of kyanite at ambient pressure: An X-ray powder diffraction study up to 1000 °C

“…Winter and Ghose (1979) collected single-crystal X-ray data at 25, 400, 600 and 800 C, from which they determined the unit-cell dimensions of kyanite. Their limited data, however, showed apparent deviation from the trends defined by Skinner et al (1961), especially at high temperatures. Recently, Gatta et al (2006) carried out a neutron powder diffraction study at ambient temperature and in the temperature range of 600e1200 C. Putting aside the large gap between room temperature and 600 C, the thermal expansion coefficients obtained in this study are generally in good agreement with those of Winter and Ghose (1979) but the changes with temperature of the unit-cell angles of kyanite are not.…”

“…Consequently, in order to achieve good data quality, kyanite should be probed by X-ray radiation of long wavelength whenever possible. Both this study and that of Skinner et al (1961) used copper as the X-ray target. As shown in Fig.…”

“…Solid circles, data collected at different temperatures in the 1st series of experiments; shaded circles, data collected at different temperatures in the 2nd series of experiments; empty triangles, data from Gatta et al (2006); pluses, data from Winter and Ghose (1979); diamonds, data from Skinner et al (1961). For most data, error bars are smaller than or equal to symbol size.…”

“…In contrast, the thermal expansion of kyanite at high temperatures has been investigated in only three experimental studies (Skinner et al, 1961;Winter and Ghose, 1979;Gatta et al, 2006). Skinner et al (1961) collected X-ray diffraction data on a kyanite powder that was heated up to 1055 C, but they calculated the unitcell parameters by using only six d-spacings.…”

“…Skinner et al (1961) collected X-ray diffraction data on a kyanite powder that was heated up to 1055 C, but they calculated the unitcell parameters by using only six d-spacings. Unfortunately, kyanite has low symmetry (space group P1), and the determination of six unknowns (a, b, c, a, b and g) from six independent equations is questionable.…”