Hydrothermal synthesis and characterization of CaSO₄ pseudomicrorods

Abstract

Calcium sulphate (CaSO₄) pseudomicrorods have been synthesized by a low-temperature hydrothermal method using CaSO₄ 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) Å, b = 6.9939(5) Å and c = 6.2434(4) Å. Scanning electron microscopy images show that the pseudomicrorods have diameters of about 0.2–2.5 µm and lengths of about 2–10 µm. Fourier transform infrared spectroscopy shows a strong doublet near 609 and 681 cm⁻¹ arising from ν₄ bending vibrations. The strongest band observed at 1132 cm⁻¹ is associated with ν₃ stretching vibrations. The band near 420–450 cm⁻¹ is attributed to ν₂ bending vibrations. The Raman spectrum exhibits an intense peak at 1008 cm⁻¹ associated with the 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.

Keywords:

• hydrothermal
• CaSO₄ pseudomicrorods
• FT-IR
• Raman spectroscopy
• photoluminescence

Acknowledgements

HN thanks Dr. S.C. Sharma, Vice Chancellor, Tumkur University, Tumkur for the constant support and encouragement, also thanks UGC for awarding a minor research project. RPSC thanks Dr. H.S. Maiti, Director CGCRI, and Dr. Ranjan Sen, Head of Glass Technology Laboratory CGCRI, for their constant support and encouragement.