Tellurium
Tellurium is a non-metallic element with many properties similar to selenium and sulfur. It is silvery-white and lustrous in solid form and dark grey in powder form. Tellurium’s industrial uses include, as an additive to improve the machinability of steel and copper alloys, as a catalyst in chemical processes and in the manufacture of rubber. It is a p-type semiconductor and its conductivity is sensitive to light exposure. Tellurium compounds (tellurides) are semiconducting materials and used for photoreceptors in copiers and solar cells. Tellurium is soluble in sulfuric acid, nitric acid, potassium hydroxide and potassium cyanide solution. It is insoluble in water.
Crystal Structure: Hexagonal; at 25 oC, a = 0.44565 nm and c = 0.59268 nm.
Density: 6.237 g/cm3 at 25 oC. Temperature dependence:
solid (0 to 450 oC), ρ = 6.250 - 0.000261 T
liquid (450 to 1000 oC), ρ = 6.170 - 0.000777 T.
Melting Point: 449.5 oC
Boiling Point: 989.8 oC
Coefficient of Linear Thermal Expansion: 18.2 µm/m ⋅ K at 20 oC
Specific Heat: 0.201 kJ/kg ⋅ K at 25 oC
Latent Heat of Fusion: 86.113 kJ/kg
Latent Heat of Vaporization: 446.43 kJ/kg
Thermal Conductivity:Polycrystalline, between 5.98 and 6.02W/m⋅K at about 20to28 oC.
Single crystals, 3.3 W/m ⋅ K ∥ to c axis, 2.1 W/m ⋅ K ⊥ to c axis.
Electrical Resistivity: Polycrystalline, between 1 and 50 mΩ ⋅ m at 25 oC.
Single crystals, at 20oC: 5mΩ⋅m ∥ to c axis, 1.5mΩ⋅m ⊥ to c axis.
Magnetic Susceptibility: At 18 oC, -39.5 x 10-6 in cgs units
Index of Refraction: Vapor, 1.002495 at λ = 589 nm; ∥ to plane of incidence, 1.9 to 2.4
at 350 to 400 nm ⊥ to plane of incidence, 1.7 to 2.7
Tensile Strength: Approximately 11 MPa
Hardness: 25 HB, 2.3 Mohs
Elastic Modulus: Tension (single crystals): 42.57 GPa ∥ to c axis
20.45 GPa ⊥ to c axis.
Shear: (Polycrystalline), 15.16 GPa
Liquid Surface Tension: 186 mN/m at 450 oC
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