Control of Optical Reflection in Ca2MgWO6 by Co and Mo Doping
Kazuki Yamaguchi1,2, Kohei Minagawa1,2, Ryohei Oka3
1Department of Chemistry and Biotechnology, Faculty of Engineering, Tottori University, 4-101, Koyama-cho Minami, Tottori 680-8552, Japan.
Researchers developed new, non-toxic inorganic red pigments by modifying the band structure of Ca2(Mg, Co)WO6. Doping with molybdenum (Mo6+) narrowed the bandgap, shifting color from pale orange to dark red.
Area of Science:
- Materials Science
- Solid-State Chemistry
- Inorganic Pigments
Background:
- Current inorganic red pigments often contain harmful elements.
- Developing safe and vibrant red pigments is crucial for various industries.
- Understanding the relationship between band structure and color is key.
Purpose of the Study:
- To synthesize novel inorganic red pigments without hazardous elements.
- To investigate the effect of molybdenum (Mo6+) doping on the band structure and color of Ca2(Mg, Co)WO6.
Main Methods:
- Synthesized Ca2Mg1-xCoW1-yMoO6 samples using a sol-gel method with citric acid.
- Characterized crystal structure, optical properties, and color of the synthesized materials.
- Analyzed the formation of a new conduction band due to Mo6+ doping.
Main Results:
- Successfully formed a Ca2Mg1-xCoW1-yMoO6 solid solution.
- Observed visible light absorption below 600 nm, shifting to longer wavelengths with increased Mo6+ content.
- Achieved a color transition from pale orange to dark red (hue angle < 35°) by narrowing the bandgap.
Conclusions:
- Mo6+ doping effectively narrows the bandgap energy of Ca2(Mg, Co)WO6 by forming a Co3d-W5d-Mo4d hybrid orbital.
- The color of the pigment can be precisely controlled by adjusting the Mo6+ content and thus the bandgap.
- This study presents a promising route for developing novel, safe, and tunable inorganic red pigments.
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