The thermal expansion of synthetic aluminosilicate-sodalites, M 8(Al6Si6O24)X 2

1432-2021

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Geosciences

Physics

Abstract Thermal expansion data, determined by powder X-ray diffraction methods are presented for 11 members of the (Li,Na,K,Rb)8(Al6Si6O24)Cl2 solid solution series, 3 members of the (Na,K)8(Al6Si6O24)Br2 solid solution series and Na8(Al6Si6O24)I2. Only the latter showed a discontinuity in its expansion curve at 810° C wigh a mean linear expansion coefficient of 22.0×10−6 °C−1 below and 7.7×10−6 °C−1 above the discontinuity. The mean expansion coefficients from 0° to 500° C decrease gradually over the range of room temperature cell edges from 8.4 to 8.89 Å, then increase up to a cell edge of 9.01 Å above which they decrease sharply and extrapolate to a zero coefficient at 9.4 Å. These variations may be related to the expansion characteristics of the bonds between the cavity cations and cavity anions in different sodalites. The aluminosilicate-sodalites which show a discontinuity in their thermal expansion curves are those with large cavity anions, I− or SO 4 2− ; the discontinuity is believed to occur at the point when the x-coordinate of the cavity cation becomes 0.25.

Electronic Resource