Tungsten(IV) oxide, WO₂, is a compound of tungsten and oxygen. It appears as a bronze-colored solid with a metallic luster. Unlike the more common tungsten trioxide (WO₃), which is yellow, WO₂ features tungsten in a lower +4 oxidation state. Its crystal structure is typically a distorted rutile form, contributing to its unique properties.

(tungsten ii oxide)

WO₂ exhibits metallic electrical conductivity, a key characteristic distinguishing it from the insulating or semiconducting behavior of WO₃. This conductivity arises from the partially filled d-orbitals of tungsten(IV). WO₂ is often discussed within the context of the tungsten oxide bronzes, specifically the “tungsten bronze” phase, which refers to substoichiometric oxides like WO₃₋ₓ (where x represents oxygen deficiency). WO₂ itself can be considered part of the Magnéli phase series for tungsten oxides.

Synthesizing pure WO₂ can be challenging. Common methods include reducing WO₃ under controlled conditions using hydrogen gas or carbon monoxide at elevated temperatures (around 900-1000°C). Alternatively, thermal decomposition of ammonium paratungstate under reducing atmospheres is employed. Precise control of temperature and reducing agent concentration is vital to avoid over-reduction to tungsten metal or under-reduction to other oxides.

(tungsten ii oxide)

Chemically, WO₂ is relatively stable in air at room temperature but oxidizes slowly over time. It reacts with strong oxidizing agents and dissolves in concentrated acids. Its primary interest lies in its electrical properties. Research explores its potential in thermoelectric materials for converting heat to electricity, electrodes, and specific catalytic applications where its metallic conductivity and surface chemistry are advantageous. However, handling requires care due to its reactivity with acids and oxidizers. WO₂ represents a crucial intermediate state in tungsten oxide chemistry.
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Tungsten Oxide Powder: Key Facts & Uses

(tungsten oxide powder)

Composition: Primarily tungsten trioxide (WO₃), sometimes tungsten dioxide (WO₂). CAS 1314-35-8.

Appearance: Fine, dry powder. Color varies: yellow (common WO₃), blue (WO₂.90), violet (WO₂.72), or brown depending on stoichiometry and oxidation state.

Properties:
* High Chemical Stability: Resistant to most acids except HF; dissolves in strong alkalis.
* High Melting Point: Approximately 1473°C (WO₃).
* Low Solubility: Insoluble in water and most organic solvents.
* Semiconducting: Bandgap around 2.6-2.8 eV for WO₃.
* Electrochromic: Changes color reversibly with applied voltage (used in smart windows).
* Photocatalytic: Active under visible/UV light for reactions like pollutant degradation or water splitting.
* Gas Sensing: Sensitivity to gases like NO₂, NH₃, H₂S due to conductivity changes.

Key Applications:
1. Smart Windows & Displays: Electrochromic layers for controllable tinting.
2. Catalysis: Catalyst or support in petroleum refining, chemical synthesis, and environmental catalysis (e.g., SCR denox).
3. Gas Sensors: Detecting toxic or flammable gases in industrial safety systems.
4. Pigments: Yellow ceramic pigments and coatings.
5. Photocatalysis: Water treatment (degrading organic pollutants), hydrogen production.
6. Intermediate: Precursor for producing tungsten metal powder and tungsten carbide powders.
7. Nanomaterials: Nanorods, nanowires, and nanoparticles for enhanced functional properties.

Forms: Available as micron-sized powders and increasingly as nanoparticles (enhanced surface area/reactivity).

Handling: Fine powder. Avoid inhalation. Use appropriate PPE (dust mask, gloves). Store in a cool, dry place.

(tungsten oxide powder)

Important: Tungsten oxide powder itself is generally considered low toxicity but always consult specific Material Safety Data Sheets (MSDS/SDS) for safe handling procedures.
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Blue Tungsten Oxide What It Is

(blue tungsten oxide)

Blue Tungsten Oxide often abbreviated BTO refers to tungsten oxide compounds exhibiting a distinctive blue color Unlike the common yellow WO3 BTO possesses a mixed valence state typically containing both W⁶⁺ and W⁵⁺ ions This structure creates oxygen vacancies crucial for its unique properties

How Its Made
BTO is primarily produced through the controlled reduction of yellow tungsten oxide WO3 This involves heating WO3 under specific conditions often in a reducing atmosphere like hydrogen or with carbon The precise temperature time and reducing agent concentration determine the final composition and depth of the blue color

Where Its Used
BTO finds significant application in several advanced technologies Its primary use is as a precursor material for producing tungsten metal powders and tungsten carbide powders essential for hard metals and alloys A major growing application is in electrochromic smart windows BTOs ability to change color reversibly with applied voltage makes it valuable for coatings that control light and heat transmission in buildings It also serves as a catalyst in certain chemical processes particularly selective oxidation reactions

Why It Matters

(blue tungsten oxide)

The mixed valence state and resulting oxygen vacancies in BTO are key Its these features that enable the efficient reduction to metal powder and drive the electrochromic effect switching between blue bleached states This makes BTO a critical functional material for modern energy efficient technologies and advanced industrial materials
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Tungsten trioxide, WO₃, is a versatile and significant inorganic compound. It appears as a yellow powder or crystalline solid at room temperature. Chemically stable and insoluble in water, it exhibits fascinating properties driven by its unique structure. A key characteristic is its electrochromism: applying a small electrical voltage causes it to reversibly change color, typically from pale yellow to deep blue. This makes it vital for smart windows that dynamically control light and heat entering buildings.

(tungsten trioxide )

WO₃ is also a prominent semiconductor material. Its electrical conductivity changes dramatically when exposed to certain gases, making it an excellent base material for sensitive gas sensors, particularly for detecting pollutants like nitrogen oxides or ammonia. Furthermore, tungsten trioxide is a known photocatalyst. Under light irradiation, it can accelerate chemical reactions, useful for applications like air purification (breaking down pollutants) or water splitting for hydrogen production, though efficiency improvements are ongoing.

(tungsten trioxide )

Its thermal properties are notable too; it has a high melting point exceeding 1470°C, contributing to its stability in demanding environments. While generally considered non-toxic, standard laboratory precautions apply when handling fine powders. Beyond smart glass and sensors, WO₃ finds use in fire-retardant fabrics, X-ray shielding phosphors, and as a precursor for producing tungsten metal and carbides. Its combination of electrochromic behavior, semiconducting nature, catalytic potential, and thermal resilience ensures tungsten trioxide remains a crucial material in advanced technological applications across energy, environmental, and electronic sectors.
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Tungsten oxide refers primarily to tungsten trioxide, WO3, the most stable compound of tungsten and oxygen. It appears as a yellow crystalline solid or powder. Tungsten dioxide, WO2, is a less common bronze-colored solid. WO3 is an important n-type semiconductor material. Its electrical conductivity changes significantly with temperature and gas exposure. This makes it highly valuable for gas sensing applications, detecting pollutants like nitrogen oxides and ammonia.

(tungsten oxide )

A key property is electrochromism. Tungsten oxide can reversibly change color, typically from transparent to deep blue, upon the insertion of small ions like lithium or protons under an applied voltage. This is the principle behind smart windows, which dynamically control light and heat transmission in buildings. It also exhibits photocatalytic activity under visible light, useful for breaking down pollutants in air or water.

(tungsten oxide )

Tungsten oxide finds use in various catalysts, particularly for industrial chemical processes like selective oxidation. It serves as a pigment in ceramics and paints, providing yellow hues. Its high density and stability contribute to applications in radiation shielding. Research explores its potential in next-generation batteries and solar cells. Tungsten oxide nanoparticles are studied for enhanced performance in many of these areas. While generally stable, handling requires standard precautions for fine powders. Tungsten oxide remains a versatile material driven by its unique electronic and optical properties.
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Tungsten(VI) oxide, WO3, is a significant inorganic compound, often appearing as a yellow powder or crystalline solid. Its bright yellow color in powder form is distinctive. This material is a wide bandgap semiconductor, a property crucial for many of its technological applications. WO3 exhibits electrochromic behavior, meaning its optical properties, like color and transparency, change reversibly when a small electrical voltage is applied. This makes it the heart of smart windows, which can dynamically control light and heat transmission for energy efficiency in buildings. Its photochromic and gasochromic properties are also exploited in similar smart glass technologies and sensors. Tungsten trioxide is a versatile catalyst. It plays a vital role in industrial processes like the selective catalytic reduction (SCR) of nitrogen oxides (NOx) in exhaust gases, helping reduce air pollution. It’s also investigated for photocatalytic applications, including water splitting for hydrogen production and environmental pollutant degradation under light irradiation. Its sensitivity to various gases, like nitrogen dioxide (NO2) and hydrogen sulfide (H2S), makes it valuable for developing solid-state gas sensors for environmental monitoring and safety. Furthermore, WO3 finds use as a pigment (cadmium yellow substitute), in fireproofing fabrics, and as a corrosion inhibitor. Its stability, tunable properties via doping or nanostructuring, and diverse functionalities ensure tungsten(VI) oxide remains a key material in advanced materials science and sustainable technology development.

(tungsten vi oxide)

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Tungsten(IV) oxide, chemical formula WO₂, is a significant compound of tungsten. It appears as a bronze-colored, crystalline solid, distinct from the yellow WO₃. This material exhibits metallic conductivity, setting it apart from many other oxides. Its electrical resistivity is relatively low, typically in the range of 10⁻³ to 10⁻⁴ ohm-cm.

(tungsten iv oxide)

Structurally, WO₂ adopts a distorted rutile (TiO₂) crystal lattice. This distortion arises from the formation of tungsten-tungsten bonds, creating chains within the structure. These direct metal-metal interactions are crucial for its characteristic electrical conductivity and metallic luster. It is often classified as a bronze-phase material.

WO₂ is typically prepared by carefully reducing tungsten trioxide (WO₃) under controlled conditions. Common reducing agents include tungsten metal powder or hydrogen gas, often at elevated temperatures (e.g., 900-1000°C). Precise control of temperature and atmosphere is essential to achieve pure WO₂ and avoid further reduction or oxidation.

Its applications leverage its unique electrical properties. WO₂ is investigated for use in resistive gas sensors, particularly for detecting reducing gases like hydrogen sulfide or ammonia, where changes in its resistivity upon gas exposure provide the sensing signal. Its plasmonic properties in the infrared range make it a candidate material for applications like tunable metamaterials and thermophotovoltaics. It also finds some use as a catalyst or catalyst support.

(tungsten iv oxide)

Handling WO₂ requires caution. It is sensitive to air oxidation, especially at elevated temperatures, and can revert to WO₃. Consequently, it must often be stored and handled under inert atmospheres. Synthesis can be challenging, requiring precise conditions to prevent over-reduction to sub-oxides or tungsten metal. Despite these challenges, its distinct metallic character within the oxide family drives ongoing research interest.
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Tungsten Trioxide WO3 Essential Facts

(tungsten 4 oxide)

Chemical compound tungsten trioxide WO3 appears as a yellow powder or crystalline solid. It’s a key member of the transition metal oxide family known for unique properties. Its stability and non toxicity make it suitable for diverse applications.
Electrochromism defines WO3. Applying a small voltage alongside ions like lithium causes it to reversibly change color typically from transparent yellow to deep blue. This principle powers smart windows dynamically controlling light and heat entering buildings enhancing energy efficiency significantly.
WO3 serves as an excellent gas sensor material. Its electrical conductivity changes detectably upon exposure to gases like nitrogen dioxide ammonia or hydrogen sulfide. This sensitivity enables reliable environmental monitoring and industrial safety systems.
Photocatalytic activity allows WO3 to degrade organic pollutants under light irradiation. It also finds use as a catalyst in various chemical reactions particularly oxidation processes important in industry. Its bandgap suits visible light activation.
Synthesizing WO3 often involves calcining ammonium paratungstate or acidifying sodium tungstate solutions. Thin films vital for devices are created via sputtering sol gel processes or evaporation techniques.
Research actively explores nanostructured WO3 forms like nanowires and nanorods. These offer enhanced surface area boosting performance in sensing and catalysis. Doping with other elements further tunes its electronic and optical properties.

(tungsten 4 oxide)

Future applications target advanced energy storage systems like batteries and supercapacitors. WO3 based materials also show promise in next generation solar cells and advanced electronic devices. Its versatility continues driving materials science innovation.
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Tungsten Oxidation States Quick Reference

(tungsten oxidation states)

Tungsten (W), element 74, is a robust transition metal renowned for its high melting point and strength. A key feature of its chemistry is its wide range of achievable oxidation states, spanning from negative values up to its maximum of +6. This versatility underpins tungsten’s diverse chemical behavior and applications.

The +6 oxidation state is overwhelmingly the most stable and common for tungsten. It dominates tungsten chemistry, exemplified by compounds like tungsten trioxide (WO₃), tungstic acid (H₂WO₄), and numerous polyoxotungstate anions (e.g., WO₄²⁻, W₁₂O₄₁¹⁰⁻). These species are crucial in catalysis, pigments, and corrosion-resistant materials. Tungsten(VI) oxides form the basis of tungsten bronzes and are key in electrochromic devices.

While less prevalent than +6, the +4 and +5 oxidation states are significant. Tungsten(IV) appears in compounds like tungsten dioxide (WO₂) and tungsten disulfide (WS₂), the latter being an important solid lubricant. Tungsten(V) is often found in mixed-valence oxide clusters (e.g., in phosphotungstates) and certain halide complexes like WCl₅. These intermediate states are vital in redox catalysis and electron transfer processes.

Lower oxidation states, such as 0 (in carbonyls like W(CO)₆), +2, and +3, are less common and typically require stabilizing ligands like carbon monoxide, phosphines, or cyanide. They are primarily encountered in organometallic chemistry and cluster compounds. Tungsten can even achieve rare negative states like -2 in carbonyl anions (e.g., [W(CO)₅]²⁻).

(tungsten oxidation states)

Understanding tungsten’s oxidation state flexibility is essential. The high stability of W(VI) drives its use in hard, inert materials and mineral processing. The accessibility of lower states (especially IV and V) enables catalytic cycles in petroleum refining and pollution control. This redox chemistry, particularly within polyoxometalate frameworks, remains a vibrant area of research for energy and environmental technologies. Mastering tungsten’s oxidation states unlocks its functional potential.
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Tungsten Dioxide (WO₂) is a fascinating compound of tungsten and oxygen. Unlike the more common yellow tungsten trioxide (WO₃), WO₂ typically appears as a bronze-colored or violet solid. It exhibits metallic conductivity, meaning it conducts electricity well, which is unusual for an oxide material. This property stems from its specific crystal structure and electron configuration.

(tungsten dioxide)

WO₂ possesses a distorted rutile structure, specifically monoclinic, due to the pairing of tungsten atoms along chains. This distortion significantly influences its electronic properties. The material is known for its relatively high melting point and good chemical stability under certain conditions, typical of many refractory metal oxides.

Synthesizing WO₂ usually involves reducing tungsten trioxide (WO₃). This reduction can be achieved using hydrogen gas (H₂) at elevated temperatures (around 800-1000°C) or sometimes using carbon monoxide (CO). Precise control of temperature and reducing atmosphere is crucial to achieve the desired WO₂ phase and avoid over-reduction to tungsten metal or incomplete reduction leaving WO₃.

(tungsten dioxide)

While not as widely applied as WO₃, tungsten dioxide has unique properties driving specific uses. Its metallic conductivity makes it potentially interesting for certain electronic applications, though challenges exist. A key area is its role in photochromic and electrochromic materials. WO₂ can be a component or intermediate in thin films used for smart windows that darken in response to light (photochromic) or an applied voltage (electrochromic), helping control heat and light transmission in buildings. It also finds niche applications in catalysis for certain chemical reactions. Research continues to explore its full potential in advanced materials science.
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