Elasticity and structure of the compounds in the wollastonite (CaSiO3)-Na 2SiO 3 system: from amorphous to crystalline state.

The elastic properties and structure of four potential bioactive compounds in the CaSiO3-Na2SiO3 system were characterized by Raman and Brillouin spectroscopy at ambient conditions. The increase of Na2O content in the Na2O-CaO-SiO2 glass with the same silica content and hence polymerization was found to lower the elastic moduli with accompanied decrease of Q(0) and Q(2) species, increase of Q(1) species and negligible change of Q(3) species, corresponding to a lower and higher equilibrium constant for the disproportional reactions [Formula: see text] and [Formula: see text] (without balance), respectively. The composition-dependent variation in the shear modulus (G) of the Na2O-CaO-SiO2 glass can be attributed to the concentration change of Q(2) and probably Q(4) species; while bulk modulus (K) ascribed to the cohesion factor. The elastic moduli of the corresponding crystalline phases in this system also lower with the increase of Na2O content following two general criteria as a function of Na2O/CaO molar ratio: (1) K decreases faster than G for both the amorphous and crystalline phases and (2) both K and G decreases faster for the crystals than the glasses.