Hafnium dioxide
Hafnium(IV) oxide
CAS: 12055-23-1
Molecular Formula: HfO2
Hafnium dioxide - Names and Identifiers
| Name | Hafnium(IV) oxide |
| Synonyms | dioxohafniuM dioxohafnium Hafnium oxide Hafnium dioxide Hafnium(IV) oxide oxygen(-2) anion hafnium(+4) cation Hafniumoxidesinteredlumps Hafniumoxideoffwhitepowder HafniuM(IV) oxide, (trace Metal basis) |
| CAS | 12055-23-1 |
| EINECS | 235-013-2 |
| InChI | InChI=1/Hf.2O/rHfO2/c2-1-3 |
| InChIKey | CJNBYAVZURUTKZ-UHFFFAOYSA-N |
Hafnium dioxide - Physico-chemical Properties
| Molecular Formula | HfO2 |
| Molar Mass | 210.49 |
| Density | 9.68g/mLat 25°C(lit.) |
| Melting Point | 2810 °C |
| Water Solubility | Insoluble in water. |
| Appearance | White to brownish brown powder |
| Specific Gravity | 9.68 |
| Color | Off-white |
| Exposure Limit | ACGIH: TWA 0.5 mg/m3NIOSH: IDLH 50 mg/m3; TWA 0.5 mg/m3 |
| Merck | 14,4588 |
| Storage Condition | Room Temprature |
| Refractive Index | 2.13 (1700 nm) |
| MDL | MFCD00003565 |
| Physical and Chemical Properties | The chemical properties of hafnium oxide are similar to those of zirconia, and its activity is related to the calcination temperature. The higher the calcination temperature, the lower the chemical activity. Amorphous hafnium oxide is easily dissolved in an acid, but crystalline hafnium oxide does not react even in hot hydrochloric acid or nitric acid, and is only dissolved in hot concentrated hydrofluoric acid and sulfuric acid. After the crystalline hafnium oxide is dissolved with alkali and hydrochloric acid, it is easy to be in dilute acid. At 1100 °c, hafnium oxide and lithium hafnium acid. Hafnium oxide and alkaline earth metal hafnium oxide react with silicon dioxide and the like at temperatures above 1500 ° C. To form hafnium salts and hafnium silicates. A series of solid solutions were formed with silicon oxide above 1800 °c. The hafnium salt can be hydrolyzed to obtain Amphoteric hafnium hydroxide. The hafnium hydroxide can reach HfO(OH)2 after being dried at 100 ° C., and is converted to hafnium oxide by raising the temperature. Hf2O3 and HfO may be formed in the carbonization process, but there are few studies on this. |
| Use | is the raw material for the production of metal hafnium and hafnium alloys. Used as refractory materials, anti-radioactive coatings and catalysts. |
Hafnium dioxide - Risk and Safety
| Safety Description | S22 - Do not breathe dust. S24/25 - Avoid contact with skin and eyes. |
| WGK Germany | 3 |
| TSCA | Yes |
| HS Code | 28259085 |
Hafnium dioxide - Introduction
Insoluble in water, hydrochloric acid and nitric acid, soluble in concentrated sulfuric acid and hydrofluoric acid. Thermal expansion coefficient: 5.8 × 10-6/℃
Last Update：2022-10-16 17:12:40
Hafnium dioxide - Reference Information
| EPA chemical information | Information provided by: ofmpub.epa.gov (external link) |
| physical properties | hafnium oxide (HfO2) is a white crystal powder. Pure hafnium oxide exists in three forms, one is in the amorphous state, and the other two are crystals. When unstable compounds such as hafnium hydroxide and hafnium oxychloride are calcined at <400°C, amorphous hafnium oxide can be obtained. The hafnium oxide is continuously heated to 450~480 ℃, and it is converted into monoclinic crystal. The lattice constant is gradually increased when it is continuously heated to 1000~1650 ℃, and it is converted into a monomer of 4 hafnium oxide molecules. It starts to transform into tetragonal system when 1700~1865 ℃. Add a small amount of hafnium oxide such as magnesium oxide, calcium oxide, and manganese oxide to hafnium oxide to form a face-centered cubic lattice solid solution above 1500°C. If 8% ~ 20% calcium oxide is added to hafnium oxide, the lattice constant α will correspondingly increase from 0.5082nm to 0.5098nm. If the amount added reaches the formation of CaHfO3, the crystal structure is transformed into a rhombic crystal system. The density of monoclinic crystal hafnium oxide is 9.68g/cm3, melting point 3031K, boiling point 5673K. Hafnium oxide structure 1 |
| introduction | hafnium dioxide is white or gray powder. Insoluble in water, hydrochloric acid, nitric acid and other general inorganic acids, slowly dissolved in hydrofluoric acid to form fluorohafnium salt. It reacts with hot concentrated sulfuric acid or bisulfate to produce hafnium sulfate. Mix and heat with carbon in the presence of chlorine to obtain hafnium tetrachloride. It reacts with potassium fluosilicate to produce potassium fluorohafnium. |
| Properties | Hafnium oxide is a white cubic crystal with a specific gravity of 9.68. Melting point 2,758±25 ℃. The boiling point is about 5,400°C. The monoclinic hafnium dioxide is transformed into a tetragonal system in a sufficient oxygen atmosphere at 1,475~1,600 ℃. Insoluble in water and general inorganic acids, but slowly dissolved in hydrofluoric acid. |
| Chemical reaction | reacts with hot concentrated sulfuric acid or acid sulfate to form hafnium sulfate [Hf(SO4)2], mixed with carbon, then heated and chlorinated to form hafnium tetrachloride (HfCl4), reacts with potassium fluosilicate to form potassium hafnium fluoride (K2HfF6), and reacts with carbon above 1,500 ℃ to form hafnium carbide HfC. |
| Preparation | Hafnium oxide can be prepared by direct high temperature ignition of hafnium carbide, tetrachloride, sulfide, boride, nitride or hydrated oxide. |
| Application area | Hfnium oxide (HfO2) is the product of zirconium and hafnium separation. At present, only the United States, France and other countries produce hafnium oxide when producing nuclear-grade zirconium. China has already had the ability to produce nuclear-grade Zr and produce a small amount of hafnium oxide in the early days. But the product is scarce and expensive. As the main chemical product of hafnium, it is usually used as an optical coating material. A small amount of hafnium oxide has been tried out in high-efficiency integrated circuits. The application of hafnium oxide in high-end fields has yet to be developed. application of hafnium oxide in the field of optical coating HfO2 has a relatively high melting point, at the same time, the absorption cross section of hafnium atom is larger, the ability to capture neutrons is strong, and the chemical properties are particularly stable, so it has a very large application value in the atomic energy industry. Since the last century, optical coating has been rapidly developed. The optical characteristics of HfO2 have become more and more suitable for the requirements of optical coating technology. Therefore, the application of HfO2 in the field of coating has become more and more extensive, especially It has a relatively wide transparent band for light. When light passes through the hafnium oxide film, it absorbs less light, and most of it passes through the film through refraction. Therefore, the application of HfO2 in the field of optical coating has been paid more and more attention. |
| product characteristics and uses | hafnium dioxide (HfO2) is an oxide with a high dielectric constant. As a dielectric material, HfO2 is considered to be an ideal material to replace the traditional SiO2 dielectric layer in field effect transistors due to its high dielectric constant value (~ 20), large band gap (~ 5.5 eV) and good stability on silicon substrates. If the size of the complementary metal oxide semiconductor device is less than 1 μm, the technology using silicon dioxide as the traditional gate medium will cause a series of problems such as the increase of the heat generation of the chip and the loss of polysilicon. As the size of the transistor shrinks, the silicon dioxide The dielectric requirements must become thinner and thinner, but the value of the leakage current will increase sharply as the thickness of the silicon dioxide dielectric is smaller due to the influence of the quantum effect, therefore, a more feasible substance is urgently needed to replace silica as the gate medium. Hafnium dioxide is a ceramic material with wide band gap and high dielectric constant. Recently, it has attracted great attention in the industry, especially in the field of microelectronics. Because it is likely to replace the current silicon-based integrated circuit The core device metal oxide semiconductor field effect transistor (MOSFET) gate insulating layer silicon dioxide (SiO2) to solve the size limit problem of the development of the traditional SiO2/Si structure in the current MOSFET. |
| use | is the raw material for the production of metal hafnium and hafnium alloys. Used as refractory materials, anti-radioactive coatings and catalysts. |
| Production method | When heated to a high temperature, hafnium and oxygen directly combine to form hafnium oxide. It can also be obtained by burning its sulfate or oxalate. |
Last Update：2024-04-10 22:29:15
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