Ammonium tetraselenotungstate is an inorganic compound with the chemical formula (NH4)2WSe4.It can be used to prepare tungsten selenide films. [1]
Preparation[edit]
An excess of tungsten trioxide is added to ammonia, the reaction is filtered to obtain ammonium tungstate solution, the reaction system is filled with nitrogen, then hydrogen selenide is passed to saturation, an exothermic reaction occurs, the solution turns dark brown, and green crystals of (NH4)2WSe4 are precipitated when it is cooled.(Note: If the reaction is incomplete, the precipitation is a red crystal of (NH4)2WSe2O2.)[2]
Chemical properties[edit]
Like other ammonium salts, ammonium tetraselenatotungstate decomposes with heat. It decomposes under reduced pressure (11 mmHg N2) according to the following equation:[3]
The decomposition temperature is 230°C. The product tungsten triselenide decomposes to tungsten diselenide and selenium at 230 to 305 °C, and tungsten diselenide decomposes to monomers at 305 to 470 °C.
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