Bismuth germanate

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Structural formula
4th Bismution 3 Germanation
General
Surname Bismuth germanate
other names
  • Bismuth germanate
  • Bismuth germanium oxide
Molecular formula Bi 4 Ge 3 O 12 or Bi 12 GeO 20
External identifiers / databases
CAS number 12233-73-7
EC number 235-458-2
ECHA InfoCard 100.032.223
Wikidata Q205629
properties
Molar mass 1246 or 2900 g mol −1
Physical state

firmly

density

7.13 or 9.22 g cm −3

Melting point

1050 ° C

Refractive index

2.15 (480 nm)

safety instructions
GHS hazard labeling
no classification available
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . Refractive index: Na-D line , 20 ° C

Bismuth germanate ( BGO ) is a combination of bismuth and germanium . It has been used in scintillators since the early 1970s mainly to measure gamma radiation .

Extraction

The commercially available crystals are pulled from stoichiometric melts of bismuth (III) oxide and germanium (IV) oxide with the aid of the Czochralski process . Single crystals were first pulled by Nitsche in 1965 to replace eulytin .

properties

Bismuth germanate is a colorless solid. It has a cubic crystal structure with the space group I 4 3 d (space group no. 220) . Template: room group / 220

The scintillation light of bismuth germanate has a wavelength in the range from 375 to 650 nm with a maximum at 480 nm. Per MeV of energy of the incident gamma quantum, around 8,500 scintillation photons are produced, so the scintillation efficiency is high. BGO is quite resistant to radiation , its values ​​remain stable up to 5 · 10 4 Gy . It is mechanically quite stable and not hygroscopic . It has good resolution in the range between 5 and 20 MeV. The linear attenuation coefficient µ for the photon energy of 511 keV, which is important for positron emission tomography (PET), is 0.96 cm −1 . The time constant for a scintillation to subside is 350 ns. BGO has the highest sensitivity of all scintillators used for PET. The u. a. of atomic number and cross-section dependent photoelectric effect proportion μ r case of photon energy of 511 keV is 43%. It is the most widely used oxide based scintillator. His scintillation was discovered in 1973 by MJ Weber and RR Monchamp.

use

In addition to PET, it is also used in detectors in particle physics , space physics , and geological exploration . Arrays of bismuth germanate are also used in gamma spectroscopy .

Bi 12 GeO 20

In addition to Bi 4 Ge 3 O 12 , Bi 12 GeO 20 is another bismuth germanate known. Due to its high electro-optical coefficient of 3.3 pm / V, it is of interest for non-linear optical components (e.g. Pockels cell ) and photorefractive elements for use in the UV range. The compound has a cubic crystal structure of the sillenite type with space group I 23 (space group no. 197) . It has a melting temperature of 935 ° C and a refractive index of 2.5476. Template: room group / 197

Individual evidence

  1. ↑ a b crystals.saint-gobain.com: BGO data sheet.pdf ( Memento from March 20, 2015 in the Internet Archive ), accessed on December 28, 2015
  2. ↑ a b Konrad Kleinknecht: Detectors for particle radiation . Springer-Verlag, 2015, ISBN 3-322-82205-2 , pp. 110 ( limited preview in Google Book search).
  3. ↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
  4. ↑ Tsuguo Fukuda, Valery I. Chani: Shaped Crystals Growth by Micro-Pulling-Down Technique . Springer Science & Business Media, 2007, ISBN 978-3-540-71295-4 , pp. 118 ( limited preview in Google Book search).
  5. ↑ K. Byrappa, Tadashi Ohachi: Crystal Growth Technology . Springer Science & Business Media, 2003, ISBN 978-3-540-00367-0 , pp. 390 ( limited preview in Google Book Search).
  6. ↑ a b c d Richard C. Ropp: Encyclopedia of the Alkaline Earth Compounds . Newnes, 2012, ISBN 0-444-59553-8 , pp. 413 ( limited preview in Google Book search).
  7. ^ Nuclear Medical Imaging Techniques and Challenges, William W. Moses Lawrence Berkeley National Laboratory Department of Functional Imaging; February 9, 2005 (PDF; 9.3 MB)
  8. ^ Peter Rudolph: Handbook of Crystal Growth Bulk Crystal Growth . Elsevier, 2014, ISBN 978-0-444-63306-4 , pp. 154 ( limited preview in Google Book search).
  9. ^ MJ Weber: Luminescence of Bi4 Ge3 O12: Spectral and decay properties. In: Journal of Applied Physics. 44, 1973, p. 5495, doi : 10.1063 / 1.1662183 .
  10. ↑ D. Bravo, FJ Lopez, Opt. Mater., 1999, 13 (1), 141-5.
  11. ↑ JL Bernstein: The unit cell and space group of piezoelectric bismuth germanium oxide (Bi12GeO20). In: Journal of Crystal Growth . 1, 1967, p. 45, doi : 10.1016 / 0022-0248 (67) 90006-1 .
  12. ↑ Crystal Structure of Bi12GeO20: Reexamination of the Ge-site Vacancy Model, Eisuke Suzuki, Nobuo Iyi and Kenji Kitamura, J. Korean Phys. Soc. 32,173 doi : 10.3938 / jkps.32.173
  13. ↑ Kiyotaka Wasa: Handbook of Sputter Deposition Technology Fundamentals and Applications for Functional Thin Films, Nano-materials and MEMS . William Andrew, 2012, ISBN 1-4377-3483-9 , pp. 400 ( limited preview in Google Book Search).