Tellurium compounds, vapor pressure

Chloro(trifluoromethyl)methyleneamino tellurium pentafluoride was similarly prepared2 from tellurium chloride pentafluoride and trifluoromethyl cyanide. The product could be purified only by preparative gas chromatography on a 15% Halocarbon K-352 column. The vapor pressure of the pure compound was 50 torr at 25°. 

Tellurium tetrafluoride is a colorless crystalline solid, mp 130° with no measurable vapor pressure at room temperature. It is readily characterized by its Raman spectrum.4 The crystal structure of the compound shows TeF4 to be a polymeric bridged species In HF solution it forms salts of the type K+[TeFs ]. s... 

Tabulated Data on Vapor Pressure of Sulfur, Selenium, and Tellurium Containing Organic Compounds... 

Tellurium(IV) chloride is a white crystalline solid at room temperature. It melts at 225° and boils at 390° at 755.6 nun. pressure. It hydrolyzes readily when exposed to moist air. Solubility data indicate that it is a polar compound. Molecular-weight measurements give a value of 290.3 at 420°, which decreases as the temperature is raised to a value of 246.6 at 595°. (Formula weight of TeCU is 269.) Vapor pressure data indicate very little association. 

The thermally induced redistribution of the tellurium and selenium isotopes shown under certain conditions might be due to the formation of cesium telluride and selenide both compounds exhibit comparatively high vapor pressures (10- MPa at 1000 K, 0.1 MPa at 2000 K). 

Figure 12.10 Liquid sources are supplied by bubbling a carrier gas such as H2 or Ar through the liquid. T refers indicates tri , M designates methyl and E is for ethyl . Al, Ga, and In sources are dashed, P, As, and Sb are solid lines. Ethyl compounds are the heavy lines while methyl compounds are narrow lines. Note that the ethyl compound pressures lie below the methyl vapor pressures. Heavier metals produce lower vapor pressure organic compounds. (TMA is an exception being elose to the TEA line.) Vapor pressures of divalent metal organics such as dimethyl tellurium generally lie below the most closely-related group III or group V compound. Note that the In compounds are solids under the conditions shown above and sublime upon heating. Vapor pressures shown here are plotted from data in Ref. 3.

Metal tellurides for semiconductors are made by direct melting, melting with excess tellurium and volatilizing the excess under reduced pressure, passing tellurium vapor in an inert gas carrier over a heated metal, and high temperature reduction of oxy compounds with hydrogen or ammonia. 

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