Bismuth trioxide

Bismuth (III) oxide
IUPAC nameBismuth trioxide
Bismuth(III) oxide
Bismite (mineral)
Other namesBismite
CAS number1304-76-3
Molecular formulaBi2O3
Molar mass465.959 g/mol
Appearanceyellow crystals or powder
Density8.9 g/cm3, solid
Melting point 824°C
Boiling point 1890°C
Solubility in other solventsInsoluble
Crystal structuremonoclinic
EU classificationnot listed
NFPA 704
Flash pointnon-flammable
Related Compounds
Other anionsBismuth trisulfide
Other cationsArsenic trioxide
Antimony trioxide
Supplementary data page
Structure and
n, εr, etc.
Phase behaviour
Solid, liquid, gas
Spectral dataUV, IR, NMR, MS
Except where noted otherwise, data are given for
materials in their standard state
(at 25 C, 100 kPa)

Bismuth (III) oxide is the most important industrial compound of bismuth, and a starting point for bismuth chemistry. It is found naturally as the mineral bismite, but it is usually obtained as a by-product of the smelting of copper and lead ores. It may also be prepared by burning bismuth metal in air. Bismuth trioxide is commonly used to produce the "Dragon's eggs" effect in fireworks, as a replacement of red lead.

As a material for fuel cell electrolytes

Enlarge picture
Existence domains of the four polymorphs of Bi2O3 as a function of temperature. (a) The α-phase transforms to the δ-phase when heated above 727°C, which remains the structure until the melting point, 824°C, is reached. When cooled, the δ-phase transforms into either the β-phase at 650°C, shown in (b), or the γ-phase at 639°C, shown in (c). The β-phase transforms to the α-phase at 303°C. The γ-phase may persist to room temperature when the cooling rate is very slow, otherwise it transforms to the α-phase at 500°C.

Bismuth oxide has seen interest as a material for solid oxide fuel cells or SOFCs since it is an ionic conductor, i.e. oxygen atoms readily move through it. Pure bismuth oxide, Bi2O3 has four crystallographic polymorphs. It has a monoclinic crystal structure, designated α- Bi2O3, at room temperature. This transforms to the cubic fluorite-type crystal structure, δ-Bi2O3, when heated above 727°C, which remains the structure until the melting point, 824°C, is reached. The behaviour of Bi2O3 on cooling from the δ-phase is more complex, with the possible formation of two intermediate metastable phases; the tetragonal β-phase or the body centred cubic γ-phase. The γ-phase can exist at room temperature with very slow cooling rates, but α- Bi2O3 always forms on cooling the β-phase.

δ- Bi2O3 has the highest reported conductivity. At 750°C the conductivity of δ- Bi2O3 is typically about 1 Scm-1, about three orders of magnitude greater than the intermediate phases and four orders greater than the monoclinic phase. The conductivity in the β, γ and δ-phases is predominantly ionic with oxide ions being the main charge carrier. The α-phase exhibits p-type electronic conductivity (the charge is carried by positive holes) at room temperature which transforms to n-type conductivity (charge is carried by electrons) between 550°C and 650°C, depending on the oxygen partial pressure. It is therefore unsuitable for electrolyte applications. δ- Bi2O3 has a defective fluorite-type crystal structure in which two of the eight oxygen sites in the unit cell are vacant. These intrinsic vacancies are highly mobile due to the high polarisability of the cation sub-lattice with the 6s2 lone pair electrons of Bi3+. The Bi-O bonds have covalent bond character and are therefore weaker than purely ionic bonds, so the oxygen ions can jump into vacancies more freely.

The arrangement of oxygen atoms within the unit cell of δ- Bi2O3 has been the subject of much debate in the past. Three different models have been proposed. Sillen (1937) used powder X-ray diffraction on quenched samples and reported the structure of Bi2O3 was a simple cubic phase with oxygen vacancies ordered along<111>, i.e. along the cube body diagonal (Figure 2a). Gattow and Schroder (1962) rejected this model, preferring to describe each oxygen site (8c site) in the unit cell as having 75% occupancy. In other words, the six oxygen atoms are randomly distributed over the eight possible oxygen sites in the unit cell. Currently, most experts seem to favour the latter description as a completely disordered oxygen sub-lattice accounts for the high conductivity in a better way.

Willis (1965) used neutron diffraction to study the fluorite (CaF2) system. He determined that it could not be described by the ideal fluorite crystal structure, rather, the fluorine atoms were displaced from regular 8c positions towards the centres of the interstitial positions (Figure 2c). Shuk et al. (1996) and Sammes et al. (1999) suggest that because of the high degree of disorder in δ- Bi2O3, the Willis model could also be used to describe its structure.

Enlarge picture
(a) Sillen model; vacancies ordered along<111>, (b) Gattow model; vacancies completely disordered in oxygen sub-lattice, with each oxygen site having 75% occupancy, (c) Willis model; oxygen atoms displaced from regular 8c sites (for example, the atom marked A in (b)) along<111> to 32f sites. The Bi3+ ions labelled 1-4 in (c) correspond to those labelled 1-4 in (b).

In addition to electrical properties, thermal expansion properties are very important when considering possible applications for solid electrolytes. High thermal expansion coefficients represent large dimensional variations under heating and cooling which would limit the performance of an electrolyte. The transition from the high-temperature δ- Bi2O3 to the intermediate β- Bi2O3 is accompanied by a large volume change and consequently, a deterioration of the mechanical properties of the material. This, combined with the very narrow stability range of the δ-phase (727-824oC), has led to studies on its stabilization to room temperature.

Bi2O3 easily forms solid solutions with many other metal oxides. These doped systems exhibit a complex array of structures and properties dependent on the type of dopant, the dopant concentration and the thermal history of the sample. The most widely studied systems are those involving rare earth metal oxides, Ln2O3, including yttria, Y2O3. Rare earth metal cations are generally very stable, have similar chemical properties to one another and are similar in size to Bi3+, which has a radius of 1.03 Å, making them all excellent dopants. Furthermore, their ionic radii decrease fairly uniformly from La3+ (1.032 Å), through Nd3+, (0.983 Å), Gd3+, (0.938 Å), Dy3+, (0.912 Å) and Er3+, (0.89 Å), to Lu3+, (0.861 Å) (known as the ‘lanthanide contraction’), making them useful to study the effect of dopant size on the stability of the Bi2O3 phases.


  • Shannon, R. D., 1976 Acta Crystallographia A32:751
  • Sammes, N. M., Tompsett, G. A., Cai, Z. H., 1999, Solid State Ionics 121:1-4
  • Mairesse, G., Abraham, F., Nowogrocki, G., 1993, Journal of Solid State Chemistry 103:2
  • Shuk, P., Wiemhofer, H.D., Guth, U., Gopel, W., Greenblatt, M., 1996 Solid State Ionics 89:3-4
  • Willis, B. T. M., 1965 Acta Crystallographia 18:75
  • Gattow, G., Schroder, H., 1962 Zeitschrift Für Anorganische Und Allgemeine Chemie 318:197
  • Sillen, L. G. 1937 Ark. Kemi. Mineral. Geol. 12A:1
  • Harwig, H. A., Gerards, A. G., 1978, Journal of Solid State Chemistry 26:265
  • Harwig, H. A., 1978 Z. Anorg. Allg. Chem 444
IUPAC nomenclature is a system of naming chemical compounds and of describing the science of chemistry in general. It is developed and kept up to date under the auspices of the International Union of Pure and Applied Chemistry (IUPAC).
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Bismite is a bismuth oxide mineral, bismuth trioxide or Bi2O3. It is a monoclinic mineral, but the typical form of occurrence is massive and clay-like with no macroscopic crystals. The color varies from green to yellow.
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In physics, density is mass m per unit volume V—how heavy something is compared to its size. A small, heavy object, such as a rock or a lump of lead, is denser than a lighter object of the same size or a larger object of the same weight, such as pieces of
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boiling point of a liquid is the temperature at which the vapor pressure of the liquid equals the environmental pressure surrounding the liquid.[1][2][3][4]
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Solubility is a physical property referring to the ability for a given substance, the solute, to dissolve in a solvent.[1] It is measured in terms of the maximum amount of solute dissolved in a solvent at equilibrium. The resulting solution is called a saturated solution.
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crystal structure is a unique arrangement of atoms in a crystal. A crystal structure is composed of a motif, a set of atoms arranged in a particular way, and a lattice. Motifs are located upon the points of a lattice, which is an array of points repeating periodically in three
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monoclinic crystal system is one of the 7 lattice point groups. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal length, as in the orthorhombic system. They form a rectangular prism with a parallelogram as base.
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ion is an atom or molecule which has lost or gained one or more electrons, making it positively or negatively charged. A negatively charged ion, which has more electrons in its electron shells than it has protons in its nuclei, is known as an anion
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Bismuthinite is a mineral consisting of bismuth sulfide (Bi2S3). It is an important ore for bismuth. The crystals are steel-grey to off white with a metallic luster. It is soft enough to be scratched with a fingernail and rather dense.
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ion is an atom or molecule which has lost or gained one or more electrons, making it positively or negatively charged. A negatively charged ion, which has more electrons in its electron shells than it has protons in its nuclei, is known as an anion
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Arsenic trioxide is the most important commercial compound of arsenic, and the main starting material for arsenic chemistry. It is the highly toxic byproduct of certain kinds of ore processing, for example gold mining.
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Antimony trioxide is the chemical compound with the formula Sb2O3. It is the most important commercial compound of antimony.


As the primary oxide of antimony, Sb2O3
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This page provides supplementary chemical data on bismuth(III) oxide.

Material Safety Data Sheet

  • MSDS from SIRI

Structure and properties

Structure and properties
Index of refraction, nD ?
Dielectric constant, εr
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Mass spectrometry (previously called mass spectroscopy ()[1] or informally, "mass-spec" and MS) is an analytical technique used to measure the mass-to-charge ratio of ions.
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standard state of a material is its state at 1 bar (100 kilopascals exactly). This pressure was changed from 1 atm (101.325 kilopascals) by IUPAC in 1990.[1] The standard state of a material can be defined at any given temperature, most commonly 25 degrees Celsius,
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3, 5
(mildly acidic oxide)
Electronegativity 2.02 (scale Pauling)
Ionization energies
(more) 1st: 703 kJmol−1
2nd: 1610 kJmol−1
3rd: 2466 kJmol−1
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