X-ray, SEM, Raman and IR studies of Bi2W2O9 prepared by Pechini method

Formation of Bi2W2O9 has been monitored by X-ray powder diffraction, SEM, and Raman and IR spectra. These methods show that more stable Bi2WO6 tungstate is formed at low temperatures. Significant amount of Bi2W2O9 starts to form at about 650 °C and synthesis of Bi2W2O9 is completed after firing the material during 1 h at 850 °C. The crystallites have plate-like shape with the thickness of about 60–300 nm for the samples synthesized at 800 °C. Raman and IR studies revealed weak decrease of the WO6 tilting with decreasing crystallite size.