Tricalcium Silicate Ca₃O[SIO₄]: The monoclinic superstructure

Abstract

Crystals, free from twinning, of the monoclinic phase of tricalcium silicate exhibiting superstructure reflections have been obtained. Crystal data are: a = 33.083(8), b = 7.027(2), c = 18.499(4) Ä, β = 94.12(2)°, Ζ = 36 χ Ca2.89Mgo.i ι 0Si0 4 , V = 4289 Ä 3 . The structure analysis was carried out using 3886 independent reflection intensities measured on a single-crystal diffractometer. The unit cell (a = 12.242, b = 7.027, c = 9.250 Ä, β = 116.04°) of the monoclinic expression of the rhombohedral average structure, contains six Ca's and a triplet of silicate tetrahedra which are successively arranged on the pseudothreefold axis. The mode of orientational disorder of these tetrahedra is found to be different from that of the corresponding tetrahedra in the rhombohedral phase R. The average structure has been successfully deconvoluted to yield the superstructure containing six triplets of tetrahedra in its cell; the structure has been refined to R = 9.9% (13.6% for 2818 superstructure reflections, and 5.9% for average structure). With regard to the mode of orientational disorder, the tetrahedra of certain triplets of the superstructure determined are similar with those of R, while others share features with those of the triclinic phase Τ (Golovastikov et al., 1975). Thus the orientational disorder of the tetrahedra that characterizes the superstructure has features intermediate between those of R and T. The coordination number of the Ca atoms (mean Ca -Ο = 2.41 Ä) is in the range 6.0 ~ 7.12, giving an overall average 6.15 which is also intermediate between those of R and T.

Crystal structure refinement and hydration behaviour of 3CaO·SiO2 solid solutions with MgO, Al2O3 and Fe2O3

“…The structure data of Golovastikov et al 18 (C 3 S triclinic; ICSD = 4331) and Nishi et al 19 (C 3 S monoclinic; ICSD = 64759) were used for the refinement. The lattice parameters and changes of lattice parameters of doped C 3 S in comparison with pure C 3 S are given in Tables 3-5.…”

Research review of cement clinker chemistry

“…The analysis of the crystal structure of C 3 S has been mainly based on powder XRD, DTA and optical microscopy. Only three polymorphic structures (R, M3 and T1) of C 3 S have been determined by synthesizing single crystals [2][3][4][5]. In order to perform accurate Rietveld quantitative phase analysis (QXRD), several studies in the last decade have focused on the crystal structure of alite [6][7][8][9][10].…”

A transmission electron microscopy study of radiation damages to β-dicalcium (Ca2SiO4) and M3-tricalcium (Ca3SiO5) orthosilicates

“…All Ca are linked to oxygen via distorted CaOx polyhedra, with a coordination number x varying between 6 and 7.12, with an average of 6.15 [37]. And always according to Nishi and Tak euchi, the CaeO bond lengths vary between 2.20 Å and 3.00 Å and the average bond length is of 2.407 Å [37].…”

“…According to Jost et al the mean CaeO bond length is of 2.50 Å [34]. According to the Rietveld analysis of the diffraction profiles performed for b-C 2 S by Mumme et al [35], the [37,38]. Regarding the distribution of Ca atoms in this average unit cell, crystallographic studies tell us that along the monoclinic b <M> axis there is a succession of pure Ca atomic planes (y ¼ 1/4, 3/4) and of mixed atomic planes (y ¼ 0, 1/2) in the sense that they contain Ca, Si and O atoms with the O atoms either covalently bound to Si or ionically bound to Ca [3].…”

“…Regarding the distribution of Ca atoms in this average unit cell, crystallographic studies tell us that along the monoclinic b <M> axis there is a succession of pure Ca atomic planes (y ¼ 1/4, 3/4) and of mixed atomic planes (y ¼ 0, 1/2) in the sense that they contain Ca, Si and O atoms with the O atoms either covalently bound to Si or ionically bound to Ca [3]. All Ca are linked to oxygen via distorted CaOx polyhedra, with a coordination number x varying between 6 and 7.12, with an average of 6.15 [37]. And always according to Nishi and Tak euchi, the CaeO bond lengths vary between 2.20 Å and 3.00 Å and the average bond length is of 2.407 Å [37].…”