The Thermal Decomposition of Ammoniu Metatungstate

The thermal decomposition of ammoniu metatungstate(AMT)involved several steps in inert atmosphere: (i)That is release of crystal water between 25°C and 200°C resulte in dehydrated AMT. (ii) The formation of an amorphous phase between 200°C and 380 °C.

(iii) It's from which hexagonal WO3 form between 380 °C and 500 °C. (iv) Then it's which transform the more stable WO3 between 500°C and 600 °C. A difference in air that the formed NH3 ignited with an exothermic heat effect, and nitrous oxides formed as combustion products. The thermal behavior of AMT was similar to ammonium paratungstate (APT), (NH4)10[H2W12O 42]•4H2O, the main difference is the lack of dry NH3 between 170°C and 240°C .

 

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