The pure products of bismuth oxide powder are α-type, β-type, and δ-type. Bismuth oxide formula is Bi2O3.
Bismuth Oxide Properties:
Alpha type Bi2O3 is a yellow monoclinic crystal, and relative density is 8.9, melting point is 825 ℃, soluble in acid, insoluble in water, and alkali. The β-type is a bright yellow to orange, cubic crystal system, relative density 8.55, melting point 860 ℃, soluble in acid, insoluble in water. It is easily reduced to metallic bismuth by hydrogen, hydrocarbons, etc. δ-Bi2O3 is a unique material with a cubic fluorite-type structure, and 1/4 of the oxygen ion positions in the crystal lattice are vacant, so it has very high oxygen ion conductivity.
Bismuth Oxide Preparation:
1. To the bismuth nitrate solution (80-90 °C), add a sodium hydroxide aqueous solution without carbon dioxide dropwise and mix. The solution remains alkaline during precipitation, forming a white, volume-expanding bismuth oxide hydrate Bi (OH) 3 precipitate. This solution is heated and dehydrated into yellow bismuth trioxide after slight stirring. After decantation and washing with water, filtration, and drying, the finished bismuth oxide is prepared.
2. Under a nitrogen atmosphere, to a 0.1mol / L bismuth nitrate solution (at 80 to 90 °C) dissolved in 1mol / L nitric acid is added dropwise a 1.5mol / L sodium hydroxide aqueous solution free of carbon dioxide to mix them. The solution remains basic during precipitation. Although a white, volume-expanded bismuth oxide hydrate Bi (OH) 3 precipitates, it is dehydrated to a pale yellow bismuth trioxide after stirring in the hot solution for a while. Decant and wash 15 times with water free of air and carbon dioxide, and then filter and dry.
3. After melting the bismuth metal into the graphite crucible and melting, under the flow of oxygen, an arc is formed between the graphite electrode and the metal liquid surface to be heated and oxidized. To ensure adequate oxygen supply, the crucible should be placed in a large container, and oxygen should be continuously supplied. The reaction temperature is 750-800 °C, and β-bismuth trioxide with a purity of 99.8% or more is rapidly produced. After the product is quenched in water or on a cold metal plate, a high-temperature phase β-type product can be obtained.
4. Slowly add Bi (NO3) 3 · 5H2O acid solution (20g dissolved in 2mol / L HNO3) slowly to the excess sodium carbonate solution and stir vigorously. The Bi2O3CO3 precipitate is obtained, filtered, washed, and dried. Place it in an aluminum boat and heat it in the air at 650K for about 1.5h to get β-Bi2O3.
5. Burn the basic bismuth nitrate at 400 - 500 ℃ to remove NO3- ion for about (3 - 4h):
2BiONO3 = Bi2O3 + NO + NO2 + O2
After the burning is completed, it will turn into lemon-yellow after cooling, which is the finished product.
6. Wash the surface of 16kg 99.9% industrial bismuth with a small amount of dilute nitric acid, and then remove the surface nitric acid with conductive water. Then add 1: 1 high-purity nitric acid (35kg of nitric acid with a relative density of 1.42 plus 20L of conductive water), add it with 1μL, and continue the reaction for 10min after the addition.
After a little cooling, it is filtered, the filtrate is heated to 65 - 70 ℃, evaporated and concentrated to a relative density of 1.9, cooled and crystallized, spin-dried to obtain bismuth nitrate. Dissolve the obtained bismuth nitrate into a dilute solution with conductive water, and break down with stirring, and let it stand to make the basic bismuth nitrate completely precipitate. , Crushed, burned at 500 ℃ for 7-8 hours, crushed after a little cold, then burned for 4-5 hours, after cooling, 99.99% of high-purity bismuth oxide powder is obtained.
Bismuth Oxide Uses:
Bismuth oxide powder is used to prepare bismuth salt, and it is also used as electronic ceramic powder material, electrolyte material, photoelectric material, high-temperature superconducting material, catalyst. As an important additive in electronic ceramic powder materials, bismuth oxide powder generally requires purity of 99.15% or more. The main applications are zinc oxide varistors, ceramic capacitors, ferrite magnetic materials, glaze rubber compounding agents, red glass compounding agents, etc.
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