Influence of cetyltrimethylammonium bromide on the morphology of AWO 4 (A = Ca, Sr) prepared by cyclic microwave irradiation

Abstract

AWO 4 (A = Ca, Sr) was prepared from metal salts [Ca(NO 3) 2·4H 2O or Sr(NO 3) 2], Na 2WO 4·2H 2O and different moles of cetyltrimethylammonium bromide (CTAB) in water by cyclic microwave irradiation. The structure of AWO 4 was characterized by X-ray diffraction (XRD) and selected area electron diffraction (SAED). Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) revealed the presence of nanoparticles in clusters with different morphologies; spheres, peaches with notches, dumb-bells and bundles, influenced by CTAB. Six Raman vibrational peaks of scheelite structure were detected at 908, 835, 793, 399, 332 and 210 cm −1 for CaWO 4 and 917, 833, 795, 372, 336 and 192 cm −1 for SrWO 4, which are assigned as ν 1(A g), ν 3(B g), ν 3(E g), ν 4(B g), ν 2(A g) and ν f.r.(A g), respectively. Fourier transform infrared (FTIR) spectra provided the evidence of W–O stretching vibration in [WO 4] 2− tetrahedrons at 793 cm −1 for CaWO 4 and 807 cm −1 for SrWO 4. The peaks of photoluminescence (PL) spectra were at 428–434 nm for CaWO 4, and 447–451 nm for SrWO 4.