Silver(I) selenide

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Silver(I) selenide
Silver(I) selenide
Names
Other names
Identifiers
ECHA InfoCard 100.013.727
Properties
Ag2Se
Molar mass 294.7 g/mol
Density 8.216 g/cm3, solid
Melting point 896.85 °C (1,646.33 °F; 1,170.00 K)
insoluble
Band gap 0.15 eV [1]
Structure
orthorhombic, oP12
P212121, No. 19
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Silver selenide (Ag2Se) is the reaction product formed when selenium toning analog silver gelatine photo papers in photographic print toning. The selenium toner contains sodium selenite (Na2SeO3) as one of its active ingredients, which is the source of the selenide (Se2−) anion combining with the silver in the toning process.

It is found in nature as the mineral naumannite, a comparatively rare silver mineral which has nevertheless become recognized as important silver compound in some low-sulfur silver ores from mines in Nevada and Idaho.[2][3]

Structure[edit]

Silver selenide has two crystal phases. At lower temperatures, it has an orthorhombic structure, β-Ag2Se. This orthrhombic phase, stable at room temperature, is a Narrow-gap semiconductor, with space group P212121. The exact size of the band gap has been given variously from 0.02 eV to 0.22 eV.[4]

There is also a high temperature cubic phase, α-Ag2Se.[5], which it transforms into at temperatures above 130 °C. This high temperature phase has Space group Im-3m, No. 229, Pearson symbol cI20. The phase transition increases ionic conductivity by 10,000 times to about 2 S/cm.

References[edit]

  1. ^ O. Madelung (2004). Semiconductors: data handbook. Birkhäuser. p. 461. ISBN 978-3-540-40488-0.
  2. ^ http://nevada-outback-gems.com/Reference_pages/sulfide_ores.htm Notes on naumannite.
  3. ^ Guilbert, John M.; Park Jr, Charles F. (2007-02-09). The Geology of Ore Deposits. Waveland Press. p. 557. ISBN 978-1-4786-0887-5.
  4. ^ Kirchhoff F.; Holender J.M.; Gillan M.J. (1996). "Structure, dynamics, and electronic structure of liquid Ag-Se alloys investigated by ab initio simulation". Physical Review B. 54 (1): 190–202. arXiv:mtrl-th/9602001. Bibcode:1996PhRvB..54..190K. doi:10.1103/PhysRevB.54.190.
  5. ^ An, Boo Hyun; Ji, Hye Min; Wu, Jun-Hua; Cho, Moon Kyu; Yang, Ki-Yeon; Lee, Heon; Kim, Young Keun (2009). "Phase changeable silver selenide thin films fabricated by pulse electrodeposition". Current Applied Physics. 9 (6): 1338–1340. doi:10.1016/j.cap.2008.12.017. ISSN 1567-1739.