Exploring Brannerite-Type Mg<sub>1−<i>x</i></sub><i>M<sub>x</sub></i>V<sub>2</sub>O<sub>6</sub> (<i>M</i> = Mn, Cu, Co, or Ni) Oxides: Crystal Structure and Optical Properties
Environmentally benign, highly stable oxides exhibiting desirable optical properties and high near-IR reflectance are being researched for their potential application as pigments. Mg<sub>1−<i>x</i></sub><i>M<sub>x</sub></i>V<sub>2</sub>O<...
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| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-01-01
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| Series: | Crystals |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2073-4352/15/1/86 |
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| Summary: | Environmentally benign, highly stable oxides exhibiting desirable optical properties and high near-IR reflectance are being researched for their potential application as pigments. Mg<sub>1−<i>x</i></sub><i>M<sub>x</sub></i>V<sub>2</sub>O<sub>6</sub> (<i>M</i> = Mn, Cu, Co, or Ni) oxides with brannerite-type structures were synthesized by the conventional solid-state reaction method to study their optical properties. These series exhibit structural transitions from brannerite (<i>C</i>2/<i>m</i>) to distorted brannerite (<i>P</i><inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mover accent="true"><mrow><mn>1</mn></mrow><mo>¯</mo></mover></mrow></semantics></math></inline-formula>) and NiV<sub>2</sub>O<sub>6</sub>-type (<i>P</i><inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mover accent="true"><mrow><mn>1</mn></mrow><mo>¯</mo></mover></mrow></semantics></math></inline-formula>) structures. The average color of Mg<sub>1−<i>x</i></sub><i>M<sub>x</sub></i>V<sub>2</sub>O<sub>6</sub> compounds varies from reddish-yellow to brown to dark brown. The <i>L</i>*<i>a</i>*<i>b</i>* color coordinates reveal that Mg<sub>1−<i>x</i></sub>Cu<i><sub>x</sub></i>V<sub>2</sub>O<sub>6</sub> and Mg<sub>1−<i>x</i></sub>Ni<i><sub>x</sub></i>V<sub>2</sub>O<sub>6</sub> show more red hues in color with <i>x</i> = 0.4 and <i>x</i> = 0.5, respectively. The UV–Vis diffuse reflectance spectra indicate a possible origin for these results include the ligand-to-metal charge transfer (O<sup>2−</sup> 2p-V<sup>5+</sup> 3d), metal-to-metal charge transfer (from Mn<sup>2+</sup> 3d/Cu<sup>2+</sup> 3d/Co<sup>2+</sup> 3d/Ni<sup>2+</sup> 3d to V<sup>5+</sup> 3d), band gap transitions, and d–d transitions. Magnetic property measurements revealed antiferromagnetic behavior for the compounds Mg<sub>1−<i>x</i></sub><i>M<sub>x</sub></i>V<sub>2</sub>O<sub>6</sub> (<i>M</i> = Mn, Cu, Co, and Ni), and an oxidation state of +2 for the <i>M</i> ions was deduced from their Curie–Weiss behavior. The system Mg<sub>1−<i>x</i></sub>Mn<i><sub>x</sub></i>V<sub>2</sub>O<sub>6</sub> has a NIR reflectance in the range between 40% and 70%, indicating its potential to be utilized in the pigment industry. |
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| ISSN: | 2073-4352 |