Bismuth oxide has the chemical formula Bi2O3 which is a yellow solid with melting point of 825oC. This material has alpha (>729oC pseudo-orthorombic), beta (650-729oC orthorombic), gama (629-650oC bcc) and delta (<629oC cubic) polymorphs. Bi2O3 has excellent optical and electrical properties such as wide band gap, high refractive index, high dielectric permitivity and high photoconductivity. Bi2O3 can be produced from bismuth hydroxide, bismuth carbonate and bismuth nitrate.
It can be used in medical devices (dental treatments etc), solid oxide fuel cells (SOFCs), bio medical applications (cancer imaging), glass industry as colorant, electroceramics (lead free ferroelectrics) and superconductors. Bi2O3 is a key raw material for sodium bismuth titanate based lead free piezoceramics which are alternatives for toxic lead based piezoceramics. Bi2O3 is also an important raw material for bismuth layer-structured ferroelectrics (BLSFs) which have high Curie temperatures (generally higher than 500oC). Na0.5Bi0.5TiO3, K0.5Bi0.5TiO3, Bi4TiO3, BaBi4T4O15, Bi3TiNO9 (N=Nb,Ta) are examples of bismuth based ferroelectrics.
Photocatalytic activity of bismuth oxide is another important property for water treatment applications. It can be seen that nano bismuth oxide particles (average particle size is 20 nm) have high efficiencies for degradation and mineralization of atrazine in water*. (*Sudrajat, H., Sujaridworakun, P., “Correlation between particle size of Bi2O3 nanoparticles and their photocatalytic activity for degradation and mineralization of atrazine”, Journal of Molecular Liquids, 242,2017) Nano Bi2O3 particles can be synthesized by sol-gel method. Particle size control is avaliable with this route for variable synthesis temperatures.
Some studies (Kell, Z, Ojebuoboh, F., “Producing bismuth trioxide and its application in fire assaying”, JOM, 2002) show that bismuth oxide can be a good candidate for toxic lead monoxide as a fluxing agent in fire assaying. Fire assaying process is the quantitative determination method in which metals are seperated from impurities by fusion and weighed in order to determine the amount present in ore sample.
Nanoparticle filled polymer composites have become interesting for many applications with their outstanding properties. It can be included in nanocomposites for use in electrochemical sensor applications (Khan et al, “Toward designing efficient rice shaped polyaniline-bismuth oxide nanocomposites for sensor application”, Journal of Sol-Gel Science and Technology, 76,2015). These sensors are developed for environment and healthcare applications.
The production of Bi2O3 is generally begins with the metallic bismuth. Three commercial metods are avaliable for producing bismuth oxide. In the first technique metallic bismuth powder dissolved in nitric acid, then heating process is applied for calcination bismuth nitrate. The second technique is similar to calcination method. Neutralization is added with caustic soda and 5N+ purity bismuth oxide can be produced by this tecnique. Final commercial method is direct calcination of metallic bismuth to provide formation of bismuth oxide. High quality raw materials must be used to produce high purity bismuth oxide. These raw materials and products are analysed by inductively coupled plasma optical emission spectrometry (ICP-OES), x-ray fluoresence (XRF), energy dispersive spectrometry (EDX) and glow discharge mass spectrometry (GDMS) methods. Glow discharge mass spectrometry enables direct analysis of high purity solid samples.
Entekno have producing capability of bismuth oxide with high purity (up to 4N) and controlled physical properties.
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