What is bismuth oxid?
The pure bismuth trioxide (nanopowder ) is classified into three types: a, b and d. A type is yellow, monoclinic crystals with a melting point of 825. It is soluble in both acid and water but insoluble in alkali. The b type has a bright yellow-orange tetragonal crystalline system. Relative density is 8.55. Melting point is 860. Soluble in acid, but insoluble with water. Hydrogen and hydrocarbons can be used to reduce the material into metallic bismuth. The cubic fluorite structure of dBi2O3 makes it a unique material. The crystal lattice of d-Bi2O3 is void in 1/4, which gives it a high oxygen conductivity. Bismuth Oxide is mainly used for electronic ceramic powder materials. It can also be used as photoelectric materials, superconductors at high temperatures, and catalysers. As an additive used in electronic ceramic materials, bismuth dioxide is usually required to be purer than 99.15%. Main application objects include ceramic capacitors, zinc oxide varistors, and ferrite magnet materials.
The method for synthesis of bismuth dioxide
The aqueous sodium solution without carbon dioxide, which is a solution of sodium chloride in water, was mixed with the bismuth-nitrate solution at 80-90degC. The solution stays alkaline and the white volume-swelling Bismuth Oxide Hydrate Bi(OH3) precipitates. This solution is heated, stirred and dehydrated to yellow bismuth trioxide. After decantation of water, filtering, and drying the product, bismuth dioxide, is obtained.
A 0.1 mol/L Bismuth Nitrate Solution dissolved in 1 mole/L Nitric Acid (at 80 to90deg C.) was dropped into a 1.5 mole/L NaOH aqueous solution, without any carbon dioxide. The solution is alkaline even after precipitation. The white volume-expanded bi(OH)3 bismuth oxide is precipitated, but it dehydrates and becomes light yellow after stirring the hot solution. Wash 15 times in water without carbon dioxide or air, then filter and dry.
After melting the metal bismuth in the graphite-crucible, an arc will form between the electrode graphite and the metal’s surface. This arc will heat the metal and cause it to oxidize when oxygen is flowing. For a continuous supply of oxygen to the crucible, it should be kept in a large vessel and placed on agitator. The reaction is carried out at a temperature of 750-800degC and the b bismuth trioxide is generated quickly with a purity level of 99.8%. A high-temperature b-type phase product can then be obtained by quenching the product in water or a metal plate.
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