Crystallographic Data of a New Phase of Dicalcium Silicate

Abstract

Unit‐cell parameters and the space group of a new phase of dicalcium silicate (Ca 2 SiO 4 ) were determined by using powder X‐ray diffractometry and selected‐area electron diffraction techniques. This phase could be synthesized via the dissociation of hydrothermally synthesized alpha‐Ca 2 (SiO 4 H)OH at temperatures of ∼500°‐920°C. Crystallographic data for the sample synthesized at 600°C were as follows: Ca 2 SiO 4 , monoclinic; P 2 1 / c space group; lattice parameters of a = 0.82147(9) nm, b = 0.9808(1) nm, c = 0.9741(1) nm, and β= 94.642(7)°; cell volume ( V ) of 0.7857(1) nm 3 ; Z = 8 (where Z is the number of chemical formula units in a unit cell); and a density of 2.91 g/cm 3 . The crystallographic data for samples synthesized at 800°C had slightly different unit‐cell parameters of a = 0.82124(6) nm, b = 0.97348(7) nm, c = 0.97935(7) nm, β= 94.831(5)°, and V = 0.7849(1) nm 3 . Structural relationships of the new phase with the other dicalcium silicates are discussed.