Synthesis, Characterization and Optical Behavior of Nanocrystalline CoWO₄

Area of Science:

• Materials Science
• Solid-State Chemistry
• Nanotechnology

Background:

• Nanocrystalline materials offer unique optical and electronic properties.
• Cobalt tungstate (CoWO4) is a promising material for phosphors.
• Efficient synthesis methods are crucial for practical applications.

Purpose of the Study:

• To synthesize nanocrystalline CoWO4 using mechanochemical and solid-state methods.
• To characterize the structural and optical properties of the synthesized CoWO4.
• To evaluate the potential of CoWO4 as a blue-green phosphor for LEDs.

Main Methods:

• Mechanochemical synthesis and solid-state reaction.
• X-ray diffraction (XRD) and infrared spectroscopy (IR) for structural characterization.
• Diffuse reflectance UV-visible (DRS) and photoluminescence (PL) spectroscopy for optical analysis.
• Transmission electron microscopy (TEM) for morphology studies.

Main Results:

• Mechanochemical synthesis at 850 rpm for 1 hour directly produced monoclinic CoWO4.
• Solid-state synthesis resulted in incomplete reactions.
• Crystallite sizes ranged from 20 to 180 nm.
• Optical bandgap values were between 1.89 and 2.18 eV.
• Observed blue-green emission spectra peaked at 430 nm with quantum yields up to 0.67% for optimized conditions.
• CIE color coordinates indicated blue and purple emission regions.

Conclusions:

• The mechanochemical approach is a cost-effective and efficient method for synthesizing CoWO4 blue-green phosphors.
• The synthesized CoWO4 exhibits promising optical properties for LED applications.
• Further optimization could enhance quantum yields for improved performance.