Bismuth germanate
Encyclopedia
Bismuth germanium oxide is an inorganic chemical compound with main use as a scintillator
. It forms cubic crystals.
When subjected to high energy gamma ray
s, bismuth germanate emits photon
s of wavelength
s between 375-650 nm, with peak at 480 nm. It produces about 8500 photons per megaelectronvolt of the high energy radiation absorbed. It has good radiation hardness (parameters remaining stable up to 5.104 Gy
), high scintillation efficiency, good energy resolution between 5-20 MeV, is mechanically strong, and is not hygroscopic. It has very high density, 7.13 g/cm³ and a high Z value. Its melting point is 1050 °C. It is the most common oxide-based scintillator.
Bismuth germanium oxide is used in detectors in particle physics
, aerospace
physics, nuclear medicine
, geology exploration, and other industries. Bismuth germanate arrays are used for gamma pulse spectroscopy. BGO crystals are also used in positron emission tomography
detectors.
Commercially available crystals are grown by the Czochralski process
and usually supplied in the form of cuboid
s or cylinders. Large crystals can be obtained.
Bismuth germanate has high electro-optic coefficients (3.3 pm/V for Bi12GeO20), making it useful in nonlinear optics
for building Pockels cells, and can also be used for photorefractive devices for ultraviolet
range.
Scintillator
A scintillator is a special material, which exhibits scintillation—the property of luminescence when excited by ionizing radiation. Luminescent materials, when struck by an incoming particle, absorb its energy and scintillate, i.e., reemit the absorbed energy in the form of light...
. It forms cubic crystals.
When subjected to high energy gamma ray
Gamma ray
Gamma radiation, also known as gamma rays or hyphenated as gamma-rays and denoted as γ, is electromagnetic radiation of high frequency . Gamma rays are usually naturally produced on Earth by decay of high energy states in atomic nuclei...
s, bismuth germanate emits photon
Photon
In physics, a photon is an elementary particle, the quantum of the electromagnetic interaction and the basic unit of light and all other forms of electromagnetic radiation. It is also the force carrier for the electromagnetic force...
s of wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
s between 375-650 nm, with peak at 480 nm. It produces about 8500 photons per megaelectronvolt of the high energy radiation absorbed. It has good radiation hardness (parameters remaining stable up to 5.104 Gy
Gray (unit)
The gray is the SI unit of absorbed radiation dose of ionizing radiation , and is defined as the absorption of one joule of ionizing radiation by one kilogram of matter ....
), high scintillation efficiency, good energy resolution between 5-20 MeV, is mechanically strong, and is not hygroscopic. It has very high density, 7.13 g/cm³ and a high Z value. Its melting point is 1050 °C. It is the most common oxide-based scintillator.
Bismuth germanium oxide is used in detectors in particle physics
Particle physics
Particle physics is a branch of physics that studies the existence and interactions of particles that are the constituents of what is usually referred to as matter or radiation. In current understanding, particles are excitations of quantum fields and interact following their dynamics...
, aerospace
Aerospace
Aerospace comprises the atmosphere of Earth and surrounding space. Typically the term is used to refer to the industry that researches, designs, manufactures, operates, and maintains vehicles moving through air and space...
physics, nuclear medicine
Nuclear medicine
In nuclear medicine procedures, elemental radionuclides are combined with other elements to form chemical compounds, or else combined with existing pharmaceutical compounds, to form radiopharmaceuticals. These radiopharmaceuticals, once administered to the patient, can localize to specific organs...
, geology exploration, and other industries. Bismuth germanate arrays are used for gamma pulse spectroscopy. BGO crystals are also used in positron emission tomography
Positron emission tomography
Positron emission tomography is nuclear medicine imaging technique that produces a three-dimensional image or picture of functional processes in the body. The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide , which is introduced into the body on a...
detectors.
Commercially available crystals are grown by the Czochralski process
Czochralski process
The Czochralski process is a method of crystal growth used to obtain single crystals of semiconductors , metals , salts, and synthetic gemstones...
and usually supplied in the form of cuboid
Cuboid
In geometry, a cuboid is a solid figure bounded by six faces, forming a convex polyhedron. There are two competing definitions of a cuboid in mathematical literature...
s or cylinders. Large crystals can be obtained.
Bismuth germanate has high electro-optic coefficients (3.3 pm/V for Bi12GeO20), making it useful in nonlinear optics
Nonlinear optics
Nonlinear optics is the branch of optics that describes the behavior of light in nonlinear media, that is, media in which the dielectric polarization P responds nonlinearly to the electric field E of the light...
for building Pockels cells, and can also be used for photorefractive devices for ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
range.