What is the Decomposition Temperature of Ammonium Metatungstate Hydrate?

The decomposition temperature of ammonium metatungstate hydrate is a relatively complex parameter, as it is affected by a number of factors, such as the heating rate, the atmospheric pressure, impurities, and the purity of the material. According to the information provided in the referenced article, we can categorize its decomposition temperature into several different stages and ranges:

  1. Low temperature stage (200-300°C):

o In this temperature range, ammonium metatungstate hydrate begins to gradually lose its water of crystallization and may shed most of its ammonium ions. At this time, its chemical structure begins to change, but it is not yet completely decomposed.

  1. Medium temperature stage (300-350°C):

o When the temperature rises to 300-350°C, the ammonium metatungstate hydrate may undergo a phase transition to produce stabilized tungsten oxide. The reaction at this stage further drives the decomposition process of the compound.

  1. High temperature phase (400-550°C):

o Most sources indicate that the main decomposition temperature range of ammonium metatungstate hydrate is 400-500°C. o The decomposition temperature of ammonium metatungstate hydrate is in the range of 400-550°C. In this temperature interval, ammonium metatungstate can decompose more completely into products such as tungsten oxide, ammonia and water. Specifically, when the temperature reaches about 400°C-500°C, the decomposition reaction of ammonium metatungstate is more significant under pure hydrogen atmosphere.

o It is worth noting that even when the temperature reaches 500-550°C, a small amount of ammonium root and bound water may still fail to decompose completely.

  1. Extremely high temperature stage (above 600°C):

o When the temperature exceeds 600°C, ammonium metatungstate can be completely decomposed into tungsten trioxide (WO3). At higher temperatures (e.g. 700°C), by controlling the holding time (e.g. 2 hours), products with special structures such as hollow mesoporous tungsten trioxide spheres can be obtained.

To summarize, the decomposition temperature of ammonium metatungstate hydrate is not a fixed value, but a process that changes gradually with temperature. In the experiment, the rate of decomposition reaction and product yield can be controlled by adjusting the heating conditions. Meanwhile, it should be noted that the actual decomposition temperature may be different due to the differences in experimental conditions and material purity.

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