Ah. Shen et al., THE ALPHA-BETA QUARTZ TRANSITION AT HIGH-TEMPERATURES AND PRESSURES IN A DIAMOND-ANVIL CELL BY LASER INTERFEROMETRY, The American mineralogist, 78(7-8), 1993, pp. 694-698
The alpha-beta quartz transition was observed using laser interferomet
ry at simultaneous high temperatures and high pressures up to 850-degr
ees-C and 1100 MPa in situ in a diamond-anvil cell. The alpha to beta
transition manifested itself as an abrupt collective motion in the int
erference fringes produced by the laser light reflected from the top a
nd bottom surfaces of a doubly polished quartz platelet. The beta to a
transition was observed also as an abrupt shift of the interference f
ringes, but in the opposite direction. By using the method described i
n Shen et al. (1992a) and employing the equation of state of H2O formu
lated by Haar et al. (1984), we were able to calculate transition pres
sures accurately. The transition temperatures were fitted to a quadrat
ic function of pressure, and the following result is obtained: T (degr
ees-C) = 574.3 + 0.2559P (MPa) - 6.406 x 10(-6)P2.