Molybdenum vapor pressure, high temperature

Besides the above-mentioned application for volatile, stable compounds, the technique of matrix isolation is superior to gas-phase investigation of compounds with a low vapor pressure. The vapor pressure of molybdenum hexacarbonyl, Mo(CO)6, for instance, is only 10 mbar at room temperature, which is insufficient for ordinary gas-phase infrared measurements. However, if Mo(CO)6 is flushed with a stream of matrix gas and if the final mixture is deposited as a matrix, then the density of the Mo(CO)6 molecules increases considerably. This integration effect (the deposition time varies from 5 minutes to several hours) is very important for high-temperature species and has interesting analytical applications. 

At 10 torr, a vapor pressure of 10 torr is required to produce an acceptable evaporation rate. For most metals, this temperature is in excess of 1000°C. The refractory metals, or metals with a high melting point such as tungsten, titanium, or molybdenum, are frequently used as carriers, or boats, to hold other metals during the evaporation process. To prevent reactions with the metals being evaporated, the boats may be coated with alumina or other ceramic materials. 

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