Hydrothermal synthesis and characterization of CaSO_4 pseudomicrorods

摘要

Calcium sulphate (CaSO_4) pseudomicrorods have been synthesized by a low-temperature hydrothermal method using CaSO_4 powder as a precursor and hexadecylamine as a surfactant at 180°C for at different intervals of time. The powder X-ray diffraction pattern indicates that the as-formed pseudomicrorods are of orthorhombic phase with lattice parameters a = 7.0023(4) A, b = 6.9939(5) A and c = 6.2434(4) A. Scanning electron microscopy images show that the pseudomicrorods have diameters of about 0.2-2.5 mu m and lengths of about 2-10 mu m. Fourier transform infrared spectroscopy shows a strong doublet near 609 and 681 cm~(-1) arising from v_4 (SO_4~(2-)) bending vibrations. The strongest band observed at 1132 cm~(-1) is associated with v_3 (SO_4~(2-)) stretching vibrations. The band near 420-450 cm~(-1) is attributed to V_2 (SO_4~(2-)) bending vibrations. The Raman spectrum exhibits an intense peak at 1008 cm~(-1) associated with the SO_4~(2-) mode. The photoluminescence spectrum exhibits UV bands (330, 350 nm), strong green bands (402, 436 nm) and weak blue bands (503 nm). A widening of the optical band gap was observed as the particle size decreased.