Superstructure in a triclinic phase of tricalcium silicate

A triclinic phase of tricalcium silicate (TI) was investigated using transmission electron microscopy (TEM). Electron diffraction patterns were analyzed by introducing a subcell with the cell parameters of a = 7.081 angstrom, b = 7.043 angstrom, c = 25.230 angstrom, α = 89.97°, β = 90.37°, and γ = 119.44°. It was proven that the coordinates of all the reflections can be expressed to be ha* + kb* + lc* ± m/6(a* + 2b* + 2c*), where m = 0, 1, 2, and 3. The result indicates that the structure modulation in TI is a one-dimensional type with a structural modulation normal to (122). The modulated structure could be observed in a high-resolution TEM image as wavy contrast streaking parallel to the plane with an interval of six times the (122) spacing.