Properties and structure[1][2][3][4][5]
Due to different production methods, boron phosphide is available in red and transparent, dark red and transparent, black crystals or soft, brown amorphous substances. Chemically stable. Insoluble in concentrated nitric acid, hydrochloric acid, sulfuric acid, 40ef hydrofluoric acid and their mixed acids. It is also insoluble in mixed solutions of nitric acid and hydrogen peroxide, 20- and 60-form sodium hydroxide, sodium hydroxide and bromine water, sulfuric acid and potassium sulfate. It is not corroded by boiling inorganic acids and alkalis, and has no change when heated under reflux in aqua regia. Boron phosphide has properties similar to refractory materials, similar to boron nitride and diamond. It is harder than silicon carbide and has a large energy gap. It is oxidation resistant in the air even at high temperatures of 800 to 10,000°C. effect. When boron phosphide is heated to high temperatures, it loses phosphorus and forms a light gray residue. Boron phosphide ignites in cold places in chlorine gas, while in bromine it ignites in a slightly hot state. It burns brightly in oxygen at 200°C and can be decomposed by most metals when it is red hot. Boron nitride can be generated by heating to 800°C in nitrogen containing ammonia.
Boron phosphide single crystal is a periodic group III and V compound semiconductor. The chemical formula is BP. Covalent bonding. There is a certain ionic bond component. It is a sphalerite type structure. The unit cell is composed of a face-centered cubic lattice composed of two different types of atoms. The unit cell contains two different groups of atoms, which is a compound lattice. The crystal melting constant is 0.4538nm. The density is 2.97×10akg/m3, which is an indirect band gap semiconductor. At room temperature, the bandgap width is 2.00eV. The resistivity is 10~4Q·m. The hole mobility is 5×10.2m2/(V·S), and the refractive index of ~700nm light is 3~3.5. Rong Rong accounts for >2000 C． Difficult to prepare. Boron phosphide is a chemically stable compound. It is insoluble in concentrated nitric acid, hydrochloric acid, sulfuric acid, 409S; hydrofluoric acid and their mixed acids. It is not dissolved in the mixed acid of nitric acid and hydrogen peroxide, in 20g and 60g sodium hydroxide solution, in the mixture of sodium hydroxide and bromine water, and in the mixture of sulfuric acid and potassium sulfate.
Boron phosphide is a group III-V compound composed of elements P and B. The main crystal form is cubic, recorded as C-BP, and has a zinc-blende structure. C-BP has a structure similar to diamond. As shown in Figure 7-1(a), in the BP crystal with sphalerite structure, each B atom is surrounded by 4 P atoms. These 4 nearest neighbor P atoms Distributed on the vertex corners of the regular tetrahedron, any P atom and the central B atom each contribute a valence electron to form a covalent bond, see Figure 7-1(b). In a covalent crystal with a tetrahedral structure, the four covalent bonds form an sp3 hybrid orbital based on the linear combination of the s-state and P-state wave functions. They have the same angle between them, 109. 23′, bond The length is 0.1667nm, and the lattice constant is 0:4.538A.
Cubic crystal c-BP can be stable to 2500% under high pressure, while the chain extender will decompose at about 1100% in vacuum. C-BP will partially lose phosphorus to form hexagonal boron phosphide, which has a rhombohedral structure. The crystal structure of boron phosphide with rhombohedral structure is similar to d-B. As shown in Figure 7-1(C), it is composed of boron icosahedron and the P-P diatomic chain that cross-links them.
Purpose
Used for the study of optical absorption and as superhard inorganic materials.
Application
Research shows that boron phosphide films have good light transmittance in a wide range of wavelengths and have the best rain erosion resistance among similar films, which can maximize the damage threshold velocity (DTV) of the substrate. . Compared with germanium carbide, boron phosphide has better mechanical properties. Its Knoop hardness is 47GPa, which is more than twice that of sapphire, and its elastic modulus is also as high as 270GPa. has the highest valence among compounds; compared with diamond, boron phosphide thin layers have better adhesion and are more conducive to large-area deposition; compared with DLC, boron phosphide has lower internal stress and can interact well with various base materials. Adhesion, and there is no limit to the thickness of the deposited film. Therefore, boron phosphide can become the preferred material for anti-reflective protective coatings for infrared windows that are resistant to high-speed flight.
In addition to being an infrared anti-reflection protective film that is resistant to high-speed flight, the protective effect of boron phosphide films on components in other harsh environments has also attracted increasing attention from scholars. Boron phosphide is one of the ideal materials for corrosion-resistant films in the infrared windows of submarine telescopes. Once the submarine’s telescope window goes to sea, it has been immersed in the seawater environment. The window must not only ensure high transmittance to maintain the sensitivity and resolution of the photoelectric system, but also resist corrosion from chemicals in seawater. However, the window material of the periscope, single crystal germanium (Ge), is easily corroded by seawater, and the resulting pinhole-like corrosion points greatly reduce the optical performance. The boron phosphide film has good chemical stability and corrosion resistance, which can protect the infrared window from seawater erosion and ensure the original optical performance of the infrared window.
Production method【4】
1. Phosphine method is obtained by reacting boron trichloride or boron tribromide with phosphine.
2. Phosphorus trichloride method is obtained by reacting boron trichloride with phosphorus trichloride and hydrogen.
3． Phosphorus pentachloride method is obtained by reacting boron trichloride and phosphorus pentachloride.
4. Metal phosphide method is obtained by reacting boron trichloride and metal phosphide (MP).
5. Boron iodide method is obtained by reacting boron iodide and phosphorus in carbon disulfide.
6. Metal solvent method is produced by crystallization in metal solvents.
It is obtained by saturating a melt of boron in a metal solvent with phosphorus at a temperature high enough to melt the melting point of the alloy component, and then cooling the melt.
Brief description of the main manufacturing processes
Metal solvent method uses a closed tube. One end of the tube is in a hot zone around 1200°C and is filled with a melt of solvent nickel and boron. The other end of the tube is a phosphorus reservoir that maintains a certain Temperature is used to control the pressure of phosphorus. After the molten metal rises to a sufficient temperature, the vapor pressure of phosphorus is increased, the melt is saturated with phosphorus, and then the melt is slowly cooled to the freezing point, and the solvent metal is leached away with acid. The boron phosphide crystal is obtained.
References
[1] (Soviet Union) V. Samsonov et al., Analysis of Refractory Compounds, Shanghai Science and Technology Press, February 1965, 1st edition, page 79
[2] Semiconductor Information Editorial Department, Group 3-5 Compound Semiconductor Materials Handbook, October 1973, page 36
[3] Zhou Huijiu, Dictionary of New Materials, Shanghai Science and Technology Literature Press, 1st edition, December 1996, page 331
[4] Tianjin Research Institute of Chemical Industry and others, Inorganic Salt Industry Handbook Volume 1, Chemical Industry Press, 1st edition, October 1979, page 260
[5] Zhu Jiaqi, Han Jiecai, Infrared antireflective and protective coatings, National Defense Industry Press, 2015.07, page 286
