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calcium tungstate (CaWO4) is an optical material which can be used as a host for laser light. It has a scheelite structure and luminescence and thermo-luminescence properties. It is used in fluorescent paint, photographically-used optical screen tubes, medicine, X-ray photographs and fluorescent lamps.
Chemical Reactions
CaWO4 is formed by dissolution of scheelite in HCl solutions in the presence of solid H2WO4 which covers the surface of the particles and prevents the dissolution reaction. This solid protective layer consists of two layers, the first is formed at 293 K and the second at 373 K. The solid layer is characterized by the absence of pores and can be observed on X-ray diffraction, SEM, FT-IR spectroscopy and photoluminescence measurements.
Taguchi Robust Design: Synthesis of Nanoparticles
A simple, fast and controllable synthesis of europium (III) tungstate nanoparticles was developed using a chemical precipitation reaction. The synthesis procedure variables such as tungstate concentration, cation feeding flow rate and reactor temperature were optimized to tune particle size of synthesized europium (III) tungstate.
Zinc Tungstate: Various electrolysis parameters such as zinc plate anode in sodium tungstate solution, stir rate of the electrolyte and electrolysis voltage had no significant effect on the size of produced particles. Moreover, the morphological and spectroscopic characterization was carried out on the produced product through SEM, XRD, UV-vis spectroscopy and FT-IR spectroscopy.
Strontium Tungstate: The synthesis of strontium tungstate nanocrystals with different morphologies in aqueous and poly vinyl alcohol medium was performed by controlled precipitation methods. X-ray diffraction and SEM investigations of the prepared nanocrystals showed that the average particle sizes range between 20-24 nm. Conclusion: The luminescent properties of the synthesized nanocrystals were examined at room temperatures and demonstrated strong emission around 425 nm.