Silver(I) selenide

Silver(I) selenide
Names
	Other names Naumannite
Identifiers
CAS Number	1302-09-6 ;
ECHA InfoCard	100.013.727
PubChem CID	6914520;
UNII	QZ0B90W7EQ ;
CompTox Dashboard (EPA)	DTXSID2061644 ;
Properties
Chemical formula	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)
Solubility in water	insoluble
Band gap	0.15 eV [1]
Structure
Crystal structure	orthorhombic, oP12
Space group	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

Silver selenide has two crystal phases. At lower temperatures, it has an orthorhombic structure, β-Ag₂Se. This orthorhombic 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

O. Madelung (2004). Semiconductors: data handbook. Birkhäuser. p. 461. ISBN 978-3-540-40488-0.
http://nevada-outback-gems.com/Reference_pages/sulfide_ores.htm Notes on naumannite.
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.
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.
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.

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[r1-1] O. Madelung (2004). Semiconductors: data handbook. Birkhäuser. p. 461. ISBN 978-3-540-40488-0.

[2] ttp://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.

[AnJi2009-5] 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.