Lead telluride

Template:Chembox AllOtherNamesTemplate:Chembox headerbarTemplate:Chembox IndexlistTemplate:Chembox JmolTemplate:Chembox ChEMBLTemplate:Chembox ECHATemplate:Chembox E numberTemplate:Chembox IUPHAR ligandTemplate:Chembox UNIITemplate:Chembox CompToxTemplate:Chembox headerbarTemplate:Chembox SolubilityInWaterTemplate:Chembox headerbarTemplate:Chembox headerbarTemplate:Chembox headerbarTemplate:Chembox GHS (set)Template:Chembox SDSTemplate:Chembox headerbarTemplate:Chembox Datapage checkTemplate:Chembox Footer

Lead telluride

Template:Longitem	Template:Unbulleted list
ChEBI	Template:Unbulleted list
ChemSpider	Template:Unbulleted list
DrugBank	Template:Unbulleted list
EC Number	Template:Unbulleted list
KEGG	Template:Unbulleted list
Template:Longitem	Template:Unbulleted list
RTECS number	Template:Unbulleted list
Template:Longitem	PbTe
Molar mass	334.80 g/mol
Appearance	gray cubic crystals.
Density	8.164 g/cm3
Melting point	Template:Chembox CalcTemperatures
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)
Template:Longitem	Halite (cubic), cF8
Template:Longitem	Fm3m, No. 225
Template:Longitem	a = 6.46 Angstroms
Template:Longitem	Octahedral (Pb2+) Octahedral (Te2−)
Template:Longitem	50.5 J·mol−1·K−1
Template:Longitem	−70.7 kJ·mol−1
Template:Longitem	110.0 J·mol−1·K−1
Flash point	Template:Chembox CalcTemperatures
Template:Longitem	Lead(II) oxide Lead(II) sulfide Lead selenide
Template:Longitem	Carbon monotelluride Silicon monotelluride Germanium telluride Tin telluride
Template:Longitem	Thallium telluride Bismuth telluride

File:PbTe unit cell.png

PbTe unit cell

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. 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)
• Seebeck coefficient: ~326 μV/K (undoped, at 300K), ~200 μV/K (Ag-doped)

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.

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. 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'. 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.

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

See also

• Yellow Duckling, which used a lead telluride sensor to make the first infrared linescan camera

External links

• National Pollutant Inventory Lead and compounds fact sheet
• Webelements