‌As a typical representative of refractory tungsten products, tungsten heater is deep-processed products made from pure tungsten wire or doped tungsten wire. Known as "tungsten heater" in English, they generally contain over 99.95% tungsten and have diameters ranging from ‌0.2–1.2 mm‌.

Like ammonium paratungstate, ammonium metatungstate (AMT) is also an important tungstate, with the chemical formula (NH₄)₆H₂W₁₂O₄₀·xH₂O, where x typically ranges from 0 to 23. Common forms include (NH₄)₆H₂W₁₂O₄₀·4H₂O and (NH₄)₆H₂W₁₂O₄₀·H₂O.

As a common impurity element in ammonium metatungstate (AMT), sodium primarily affects its physicochemical properties and application performance in the following ways:

Ammonium metatungstate (AMT) is an important intermediate product of the transition metal tungsten, with a molecular formula of H₂₈N₆O₄₁W₁₂, containing nitrogen, hydrogen, tungsten, and oxygen. However, in practice, besides these four elements, AMT also contains impurity elements such as Al, As, Bi, Ca, Cu, Fe, Mg, Mn, Mo, Na, Ni, Pb, Si, Sn, and Ti. The impact of aluminum on the properties of AMT is as follows: