Infrared spectra and cell dimensions of hydrothermally synthesized grandité-hydrograndite series

Abstract

The infrared (IR) absorption patterns, and the cell dimensions of the grandite-hydrograndite series have been revealed as a function of chemistry using the materials hydrothermally synthesized at temperatures between 230 and 620°C under a pressure of 100 MPa for 5 to 76 days. They were formed from the starting materials whose compositions were written as Ca₃ (Al_1−WFe_W)₂(SiO₄)_3X(O₄H₄)_X, where W is 0.2, 0.4, 0.6, 0.8 and 1.0, and X is 0, 0.2, 0.4, 0.6, 0.8 and 1.0.
The wave numbers of nine distinct IR absorption bands between 1000 cm⁻¹ and 300 cm⁻¹ decrease by 10–70 cm⁻¹ with an increase of Fe content in the H₂O-free grandite series. The absorption band near 900 cm⁻¹ and the transmission band near 700 cm⁻¹ shift toward the higher frequency side with an increase of water and a decrease of iron. The wave numbers of two absorption bands near 600 cm⁻¹ and 520 cm⁻¹ and the transmission band near 500 cm⁻¹ decrease with increases of water and iron. The ratio of the logarithmic intensity of the transmission band near 3700 cm⁻¹ to that of the absorption one near 3660 cm⁻¹ decreases remarkably with an increase of water, while it is independent of iron content in the Al-rich (W ≤0.2) and Fe-rich (W ≥0.8) grandite-hydrograndite members. On the contrary, the cell dimension of the garnet series increases with increases of both of water and iron contents. The composition of grandite-hydrograndite series can be estimated from the IR absorption patterns and the X-ray powder diffraction data.