Bismuth germanate

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Bismuth germanate (BGO, chemical formula Bi₄Ge₃O₁₂ (evlitine structure) or the less common type Bi₁₂GeO₂₀) is an inorganic chemical compound with main use as a scintillator. It forms cubic crystals.

When subjected to high energy gamma rays, bismuth germanate emits photons of wavelengths 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 germanate 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 cuboids or cylinders. Large crystals can be obtained.

Bismuth germanate has high electro-optic coefficients, making it useful in nonlinear optics for building Pockels cells, and can also be used for photorefractive devices for ultraviolet range.