Lead telluride

Lead telluride^[1]^[2]^[3]
Names
Other names Lead(II) telluride Altaite
Identifiers
CAS Number	1314-91-6^Y
ChemSpider	3591410
ECHA InfoCard	100.013.862
EC Number	215-247-1
PubChem CID	4389803
UNII	V1OG6OA4BJ^Y
CompTox Dashboard (EPA)	DTXSID5061663
Properties
Chemical formula	PbTe
Molar mass	334.80 g/mol
Appearance	gray cubic crystals.
Density	8.164 g/cm³
Melting point	924 °C (1,695 °F; 1,197 K)
Solubility in water	insoluble
Band gap	0.25 eV (0 K) 0.32 eV (300 K)
Electron mobility	1600 cm² V⁻¹ s⁻¹ (0 K) 6000 cm² V⁻¹ s⁻¹ (300 K)
Structure
Crystal structure	Halite (cubic), cF8
Space group	Fm3m, No. 225
Lattice constant	a = 6.46 Angstroms
Coordination geometry	Octahedral (Pb²⁺) Octahedral (Te²⁻)
Thermochemistry
Std molar entropy (S^⦵₂₉₈)	50.5 J·mol⁻¹·K⁻¹
Std enthalpy of formation (Δ_fH^⦵₂₉₈)	-70.7 kJ·mol⁻¹
Std enthalpy of combustion (Δ_cH^⦵₂₉₈)	110.0 J·mol⁻¹·K⁻¹
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H302, H332, H351, H360, H373, H410
Precautionary statements	P201, P202, P260, P261, P264, P270, P271, P273, P281, P301+P312, P304+P312, P304+P340, P308+P313, P312, P314, P330, P391, P405, P501
Flash point	Non-flammable
Safety data sheet (SDS)	External MSDS
Related compounds
Other anions	Lead(II) oxide Lead(II) sulfide Lead selenide
Other cations	Carbon monotelluride Silicon monotelluride Germanium telluride Tin telluride
Related compounds	Thallium telluride Bismuth telluride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is ^YN ?) Infobox references

Chemical compound

Lead telluride is a compound of lead and tellurium (PbTe). It crystallizes in the NaCl crystal structure with Pb atoms occupying the cation and Te forming the anionic lattice. It is a narrow gap semiconductor with a band gap of 0.32 eV.^[4] It occurs naturally as the mineral altaite.

Properties

Dielectric constant ~1000.
Electron Effective mass ~ 0.01m_e
Hole mobility, μ_p = 600 cm² V⁻¹ s⁻¹ (0 K); 4000 cm² V⁻¹ s⁻¹ (300 K)

Applications

PbTe has proven to be a very important intermediate thermoelectric material. The performance of thermoelectric materials can be evaluated by the figure of merit, $ZT=S^{2}\sigma T/\kappa$ , in which $S$ is the Seebeck coefficient, $\sigma$ is the electrical conductivity and $\kappa$ is the thermal conductivity. In order to improve the thermoelectric performance of materials, the power factor ( $S^{2}\sigma$ ) needs to be maximized and the thermal conductivity needs to be minimized.^[5]

The PbTe system can be optimized for power generation applications by improving the power factor via band engineering. It can be doped either n-type or p-type with appropriate dopants. Halogens are often used as n-type doping agents. PbCl₂, PbBr₂ and PbI₂ are commonly used to produce donor centers. Other n-type doping agents such as Bi₂Te₃, TaTe₂, MnTe₂, will substitute for Pb and create uncharged vacant Pb-sites. These vacant sites are subsequently filled by atoms from the lead excess and the valence electrons of these vacant atoms will diffuse through crystal. Common p-type doping agents are Na₂Te, K₂Te and Ag₂Te. They substitute for Te and create vacant uncharged Te sites. These sites are filled by Te atoms which are ionized to create additional positive holes.^[6] With band gap engineering, the maximum zT of PbTe has been reported to be 0.8 - 1.0 at ~650K.

Collaborations at Northwestern University boosted the zT of PbTe by significantly reducing its thermal conductivity using ‘all-scale hierarchical architecturing'.^[7] With this approach, point defects, nanoscale precipitates and mesoscale grain boundaries are introduced as effective scattering centers for phonons with different mean free paths, without affecting charge carrier transport. By applying this method, the record value for zT of PbTe that has been achieved in Na doped PbTe-SrTe system is approximately 2.2.^[8]

In addition, PbTe is also often alloyed with tin to make lead tin telluride, which is used as an infrared detector material.

References

^ Lide, David R. (1998), Handbook of Chemistry and Physics (87 ed.), Boca Raton, Florida: CRC Press, pp. 4–65, ISBN 978-0-8493-0594-8
^ CRC Handbook, pp. 5–24.
^ Lawson, William D (1951). "A method of growing single crystals of lead telluride and selenide". J. Appl. Phys. 22 (12): 1444–1447. doi:10.1063/1.1699890.
^ Kanatzidis, Mercouri G. (2009-10-07). "Nanostructured Thermoelectrics: The New Paradigm? †". Chemistry of Materials. 22 (3): 648–659. doi:10.1021/cm902195j.
^ He, Jiaqing; Kanatzidis, Mercouri G.; Dravid, Vinayak P. (2013-05-01). "High performance bulk thermoelectrics via a panoscopic approach". Materials Today. 16 (5): 166–176. doi:10.1016/j.mattod.2013.05.004.
^ Dughaish, Z. H. (2002-09-01). "Lead telluride as a thermoelectric material for thermoelectric power generation". Physica B: Condensed Matter. 322 (1–2): 205–223. Bibcode:2002PhyB..322..205D. doi:10.1016/S0921-4526(02)01187-0.
^ Biswas, Kanishka; He, Jiaqing; Zhang, Qichun; Wang, Guoyu; Uher, Ctirad; Dravid, Vinayak P.; Kanatzidis, Mercouri G. (2011-02-01). "Strained endotaxial nanostructures with high thermoelectric figure of merit". Nature Chemistry. 3 (2): 160–166. Bibcode:2011NatCh...3..160B. doi:10.1038/nchem.955. ISSN 1755-4330. PMID 21258390.
^ Biswas, Kanishka; He, Jiaqing; Blum, Ivan D.; Wu, Chun-I.; Hogan, Timothy P.; Seidman, David N.; Dravid, Vinayak P.; Kanatzidis, Mercouri G. (2012-09-20). "High-performance bulk thermoelectrics with all-scale hierarchical architectures". Nature. 489 (7416): 414–418. Bibcode:2012Natur.489..414B. doi:10.1038/nature11439. ISSN 0028-0836. PMID 22996556. S2CID 4394616.